MotoGP: Jorge Lorenzo wins from Valentino Rossi in Qatar
Defending MotoGP champion Jorge Lorenzo produced a dominant performance to win the opening race of the season under the floodlights in Qatar.
The Spaniard, 25, led from pole position and opened up a comfortable gap to take his 24th MotoGP victory.
Behind him a four-man battle for the podium ended with Valentino Rossi taking second on his return for Yamaha.
Debutant Marc Marquez was just edged into third, with team-mate Dani Pedrosa fourth and Briton Cal Crutchlow fifth.
Lorenzo rode a flawless race to win by nearly six seconds, but it was the performance of seven-time champion Rossi in second which will dominate the headlines.
After two wretched years in the Ducati team, the 34-year-old was back to his duelling best to come from way back in fifth with 10 laps to go to take his place on the podium.
An early mistake, with Rossi lunging wildly up the inside of Spain's Pedrosa and ending up off the track, left the Italian in seventh place but he soon made his way back through to fifth.
A burst of speed then saw him reel in and then overtake Crutchlow and Pedrosa before the veteran came out on top of an engaging fight with 20-year-old Marquez - the Spaniard who has been heralded as one of the most exciting riders to come to MotoGP in years - to take second.
A beaming Rossi was in jubilant mood at the end of the race, telling BBC Sport: "It was great fun. Second place is the best I could do as Jorge was perfect.
"But it could have been a lot easier if I hadn't made a mistake at the start. But I wanted a podium really badly so I try, try, try!
"This has been my target since last November when I returned to Yamaha and I think we can all enjoy this season."
Crutchlow had qualified in second place and was in the hunt for a podium finish until he ran wide defending from Rossi, while his British team-mate at Tech 3 Yamaha Bradley Smith had a disappointing MotoGP debut, crashing out of 11th place on lap five.
Earlier, in the Moto3 race, pre-season title favourite Luis Salom of Spain won ahead of countrymen Maverick Vinales and Alex Rins, with Briton Danny Webb in 11th place.
British rider Scott Redding came close to his first win in the Moto2 class but he was pipped in a race-long duel by another Spaniard, Pol Espargaro - last season's championship runner-up.
Qatar MotoGP results:
1 Jorge Lorenzo (Spa) Yamaha 42mins 39.802
2 Valentino Rossi (Ita) Yamaha 42:45.792
3 Marc Marquez (Spa) Honda 42:46.003
4 Dani Pedrosa (Spa) Honda 42:49.275
5 Cal Crutchlow (GB) Yamaha 42:58.566
6 Alvaro Bautista (Spa) Honda 43:01.950
7 Andrea Dovizioso (Ita) Ducati 43:04.157
8 Nicky Hayden (USA) Ducati 43:04.722
9 Andrea Iannone (Ita) Ducati 43:16.926
10 Ben Spies (USA) Ducati 43:24.710