Bolívar defeated Grêmio 3-2 on Thursday at Estádio Hernando Siles in La Paz. The result gives the Bolivian side the advantage for the return leg.
Bolívar scored through Martín Cauteruccio, Robson Matheus and Asprilla. Grêmio replied with goals from Villasanti and Tetê.
The match took place at more than 3,500 meters above sea level. Grêmio coach Luís Castro did not travel on medical advice due to health issues.
The return fixture is scheduled for next Thursday at 19h at Arena do Grêmio. Bolívar dominated much of the game with over 60 percent possession.