Match ends, Arsenal 2, West Bromwich Albion 0.
Alexandre Lacazette scored twice to earn a shaky Arsenal victory over West Brom, their third Premier League win in a row at Emirates Stadium.
The France striker - who has scored in each of those home wins - headed into an open net in the 20th minute after West Brom goalkeeper Ben Foster tipped Alexis Sanchez's free-kick onto the crossbar.
West Brom, on the night midfielder Gareth Barry broke the Premier League appearance record, felt they should have been awarded a penalty before the opener when Shkodran Mustafi brought down Jay Rodriguez with a sliding challenge.
Instead of staying on the ground following the contact, Rodriguez chose to continue but his shot was tipped onto the post by a diving Petr Cech.
After the break, Arsenal were themselves rightly awarded a spot-kick when Allan Nyom barged over Aaron Ramsey close to the byeline.
Lacazette stepped up and calmly slotted into the bottom right corner - his fourth goal since his club record £46.5m summer move from Lyon.
The Baggies caused Arsenal problems in the first half in particular, with Nacho Monreal brilliantly clearing a Rodriguez header off the line in the 38th minute.
Victory for the Gunners lifts them to seventh in the table, one point behind fourth-placed Tottenham and six behind leaders Manchester City while West Brom drop to 12th.
- Relive the action from the Emirates
- West Brom boss Pulis accuses Sanchez of 'cheating'
- More PL wins than West Ham? How much do you know about Gareth Barry?
- The latest Football Daily podcast
Luckless night for the Baggies
West Brom boss Tony Pulis cut an exasperated figure on the touchline as his poor record at the Emirates continued. He has now lost all 10 of the matches he has managed at the ground.
Pulis was furious when a penalty was not given for Mustafi's tackle on Rodriguez and also disagreed with the decision to a give a free-kick in the build-up to Lacazette's first goal, when the contact from Jonny Evans on Mohamed Elneny looked minimal.
Former Arsenal defender and BBC Radio 5 live pundit Martin Keown agreed, saying the Baggies should "definitely" have had a penalty and calling the Evans foul "doubtful".
However, Pulis was expressionless when Madley did point to the spot in the second half and, in truth, could have few complaints.
It was a foolish shoulder charge from Nyom on Ramsey after the Arsenal midfielder had shown too much pace to surge around the Cameroon defender and into the box.
Arsenal also had a penalty appeal turned down in the first half when Grzegorz Krychowiak pulled the shirt of Sanchez at a corner.
West Brom have scored just four goals this season but could easily have added to that in the first half with Rodriguez a constant threat.
As well as the Englishman's header that was cleared off the line and the shot which followed the penalty decision, he came within inches of converting a cross from the right when sliding full-stretch towards goal.
But, despite the improved attacking display, the Baggies are now five games without a victory and have won only one of 12 away league matches in 2017.
Signs of momentum for Arsenal?
As in last week's battling 0-0 draw at Chelsea, Arsenal were not at their best but they are now five games unbeaten in all competitions.
Lacazette's performance was a clear positive for manager Arsene Wenger, who also gave a start to Sanchez for only the second time this season, following the Chile international's collapsed move to Manchester City in the summer.
It was the first time the pair had started a Premier League game together and it was Sanchez who provided the assist for Lacazette's opener.
Questions have been asked of Sanchez's attitude after he failed to get his summer move, but he worked hard on his first start since the Gunners' 4-0 defeat at Liverpool.
He went close with a free-kick before the similar effort which set up the opener and won 25 of his duels, more than any other player. He was given a standing ovation by the home crowd when substituted in the 83rd minute.
Arsenal may not be showing the eye-catching form of their top-four rivals in Manchester - with City and United level on points at the top of the table - but they are slowly starting to improve after a poor start.
"There are little partnerships building in the team," Keown said.
"Sead Kolasinac looks really strong in this side. Ramsey is playing with confidence, Lacazette looks a threat and Sanchez is back in the team and looks happy to be so. That is a plus for Wenger."
Ever the professional, Barry expressed disappointment after his side fell to defeat on the night he played his 633rd Premier League game, taking him past former Manchester United winger Ryan Giggs' record.
The 36-year-old Englishman was his solid self, the most impressive moment coming when he played an excellent pass to through to Rodriguez for the Baggies' first-half penalty appeal.
Barry was congratulated by his manager, previous clubs, former team-mates and England boss Gareth Southgate before Monday's match.
"Gareth has been a wonderful professional and still is - and we hope he keeps performing like that until the end of the season," Pulis said.
Barry told BBC Sport: "It was something different this week, having a lot of media attention. It will be nice to put this milestone to bed.
"I've not really given it too much thought about who is behind me. There is so much concentration on what you are doing."
'The referee should pull it back' - what they said
Arsenal boss Arsene Wenger, speaking to BBC Sport: "They pushed us very hard, especially in the first half. They disturbed our build-up and played a very dangerous and direct game. In the second half I felt we controlled the game and did not give anything away.
"If [the West Brom penalty] had been given I would not have said it is a scandal. Looking at the decision again he made the right decision.
"You are never too honest. I believe [Rodriguez] saw an opportunity he could score."
On Lacazette: "He gets stronger in every game. Good first touch and movement. He is young and just arrived in England. The physical demands are very high."
West Brom boss Tony Pulis on the refereeing decisions: "It is part of the game and things didn't go for us today.
"The great thing [with the challenge on Rodriguez] is that everybody has seen it so I don't have to comment on it.
"We tell our players not to roll about. He still wanted to score but once he has missed the referee should pull it back. It could be a penalty and they could have a player sent off, so we not only score but are against a team down to 10 players.
"We have got to start taking chances. We have given Arsenal a good game, but we had to chase it in the second half and that suited Arsenal."
Wenger's impressive record against Pulis - the best stats
- Wenger has won all 11 of his home games against teams managed by Pulis, 10 in the Premier League and one FA Cup game at Highbury in 2005.
- West Brom have lost more away Premier League games against Arsenal (10) than against any other side.
- Lacazette became the first Arsenal player to score in his first three home league appearances for the club since Brian Marwood in September 1988.
- Lacazette also scored Arsenal's 100th penalty in the Premier League - only Liverpool (112) and Chelsea (107) have scored more.
- Arsenal have scored in all 23 of their Premier League meetings with West Brom, the best such 100% record in the division.
- Each of the Gunners' past seven home wins have come on a different day of the week.
Arsenal travel to Belarus to play BATE Borisov in the Europa League on Thursday (18:00 BST kick-off) before hosting Brighton in the Premier League on Sunday, 1 October (12:00).
Meanwhile, West Brom entertain Watford in the league on Saturday (15:00).
- 8RamseySubstituted forMaitland-Nilesat 90+3'minutes
- 7SánchezBooked at 44minsSubstituted forÖzilat 83'minutes
- 9LacazetteSubstituted forGiroudat 83'minutes
- 25DawsonBooked at 49mins
- 6EvansBooked at 35mins
- 2NyomBooked at 67minsSubstituted forPhillipsat 74'minutes
- 8LivermoreSubstituted forMorrisonat 63'minutes
- 20KrychowiakBooked at 56mins
- 4Robson-KanuSubstituted forRondónat 64'minutes
- Robert Madley
- Shots on Target
Second Half ends, Arsenal 2, West Bromwich Albion 0.
Substitution, Arsenal. Ainsley Maitland-Niles replaces Aaron Ramsey.
Foul by Sead Kolasinac (Arsenal).
Salomón Rondón (West Bromwich Albion) wins a free kick on the right wing.
Attempt saved. Aaron Ramsey (Arsenal) right footed shot from outside the box is saved in the bottom left corner. Assisted by Olivier Giroud.
Hand ball by Granit Xhaka (Arsenal).
Héctor Bellerín (Arsenal) wins a free kick in the defensive half.
Foul by Kieran Gibbs (West Bromwich Albion).
Attempt missed. Granit Xhaka (Arsenal) left footed shot from the centre of the box is too high. Assisted by Olivier Giroud.
Laurent Koscielny (Arsenal) wins a free kick in the defensive half.
Foul by Salomón Rondón (West Bromwich Albion).
Substitution, Arsenal. Mesut Özil replaces Alexis Sánchez.
Substitution, Arsenal. Olivier Giroud replaces Alexandre Lacazette.
Corner, Arsenal. Conceded by Jay Rodriguez.
Attempt blocked. Héctor Bellerín (Arsenal) right footed shot from the right side of the box is blocked. Assisted by Granit Xhaka.
Corner, Arsenal. Conceded by James Morrison.
Attempt blocked. Mohamed Elneny (Arsenal) right footed shot from the right side of the box is blocked.
Alexis Sánchez (Arsenal) wins a free kick on the left wing.
Foul by Craig Dawson (West Bromwich Albion).