Anthony Joshua and Anthony Ogogo made it four guaranteed medals for Great Britain in the boxing ring by winning their quarter-finals on Monday.
Super-heavyweight Joshua, 22, knocked down China's Zhilei Zhang in the second round and won 15-11 in the last fight of the day.
"After a nervous first fight Anthony blew the cobwebs away, was very controlled, very focused and did a great job"
Read Lennox Lewis's column
Middleweight Ogogo, 23, earlier outpointed Stefan Hartel of Germany 15-10 to make the semis.
Luke Campbell and
are also through to the last fours.
Andrew Selby (flyweight) and Fred Evans (welterweight) will fight for medals on Tuesday, while Tom Stalker (light-welterweight) goes on Wednesday.
Joshua just scraped past Cuba's Erislandy Savon in his opening bout but the result of his match against Beijing silver medallist Zhang was never in doubt.
"That medal represents a journey, a lot of hard work, but it hasn't stopped here. It is going to get tougher and I'm going to have to keep my heads on my shoulders and try to change the colour of that medal," said Joshua.
"I learned so much from my first bout and I learned so much from this one too. I'm going to go away from these Olympics a new man because the experience is unbelievable - it's character-building.
"I'm not miles better than I was when I went to the World Championships, but I have improved. It's going to be a long career and I'll never stop improving until I finish, but I'm getting better bit by bit because of the experience."
The Londoner could not miss with his left hook in the opening round and led 3-1 going into the second.
And with Zhang looking to chase Joshua's lead, he left himself open to a chopping right hand midway through the round and crumpled to the canvas.
Joshua continued to have success with his jab in the third and, while Zhang did land with some solid blows as things got desperate, the home fighter was never in trouble.
Joshua's semi-final opponent is Kazakhstan's 6ft 9in giant Ivan Dychko, a bronze medallist at last year's World Championships, who beat Canada's Simon Kean 20-6.
If Joshua gets past Dychko he will face either Azerbaijan's Magomedrasul Medzhidov, who beat him in the final of last year's Worlds, or defending Olympic champion Roberto Cammarelle for gold.
GB's Ogogo wins to secure medal
Cammarelle, 32, had a scare against the spoiling Moroccan Mohammad Arjaoui and only nicked the decision 12-11 because of a two-point penalty for his rival.
Ogogo had an easier ride against Hartel than he did in the second round, when he beat world number one Ievgen Khytrov by judges' decision.
The Lowestoft fighter was perhaps a little lucky to have a three-point lead after the first round but, fighting behind his customary high guard and landing in flurries, he did more than enough in the second and third to deserve the win.
"It feels good to be guaranteed a bronze medal, don't get me wrong, but it's not enough," said Ogogo. "I've always dreamed of becoming Olympic champion."
Ogogo fights Brazilian Esquiva Falcao, who beat Hungary's Zoltan Harcsa 14-10, in the last four.
Falcao defeated Ogogo at last year's World Championships, but the Briton was effectively fighting with one arm after aggravating a shoulder injury.
"Last time I boxed him, every time I threw the right it felt like my arm was going to come off," said Ogogo. "I've got two good arms now so I'm looking forward to doing battle with him."
Not only did Ogogo have to overcome surgery to qualify for the Olympics, seven weeks ago his mother suffered a brain haemorrhage and is still in hospital.
Anthony Joshua happy with win
"It is not just the injuries, but also mentally with the problems at home," he added. "But I don't want to cry so I am going to tough it out."
Abbos Atoev of Uzbekistan will fight Ryota Murata in the second 75kg semi.
In the lightweight division, Ukraine's Vasyl Lomachenko, the reigning Olympic featherweight champion, comfortably beat Felix Sanchez of Puerto Rico 14-9.
Lomachenko, regarded by many as the best pound-for-pound amateur boxer in the world, will not have it all his own way against Cuba's Yasnier Toledo Lopez, who looked very assured in beating Gani Zhailauov 19-11.
In the other 60kg semi-final, all-action Lithuanian Evaldas Petrauskas will fight South Korea's Soonchul Han.