Lorenzo started from pole position on Sunday at the Circuit de Catalunya and always looked in control on his Yamaha. Fellow Spaniard Dani Pedrosa was second and Australia's Casey Stoner was third.
Lorenzo leads the MotoGP standings with 165 points after the seventh race of the season. Pedrosa is second with 113 points, and Andrea Dovizioso of Italy is third with 91.
Yuki Takahashi won the 250cc category, followed by Thomas Luthi and Julian Simon.
In the 125cc category, Marc Marquez was first, with Bradley Smith second and Pol Espargaro third.
Results from the Catalan Grand Prix:
MotoGP:
1. Jorge Lorenzo (ESP/Yamaha), the 25 laps in 43:22.805, 2. Dani Pedrosa (ESP/Honda) at 4.754, 3. Casey Stoner (AUS/Ducati) 4.956, 4. Randy de Puniet (FRA/Honda) 18.057, 5. Alvaro Bautista (ESP/Suzuki) 21.361, 6. Ben Spies (USA/Yamaha) 21.503, 7. Loris Capirossi (ITA/Suzuki) 24.181, 8. Nicky Hayden (USA/Ducati) 27.941, 9. Marco Melandri (ITA/Honda) 28.046, 10. Hector Barbera (ESP/Ducati) 32.439
Overall standings
1. Jorge Lorenzo (ESP/Yamaha) 165 points, 2. Dani Pedrosa (ESP/Honda) 113, 3. Andrea Dovizioso (ITA/Honda) 91, 4. Nicky Hayden (USA/Ducati) 69, 5. Randy de Puniet (FRA/Honda) 69, 6. Casey Stoner (AUS/Ducati) 67, 7. Valentino Rossi (ITA/Yamaha) 61, 8. Ben Spies (USA/Yamaha) 59, 9. Marco Melandri (ITA/Honda) 39, 10. Marco Simoncelli (ITA/Honda) 39
125 cc
1. Marc Marquez (ESP/Derbi), the 22 laps in 40:46.315, 2. Bradley Smith (GBR/Aprilia) at 4.638, 3. Pol Esparagaro (ESP/Derbi) 4.996, 4. Sandro Cortese (GER/Derbi) 45.366, 5. Efren Vazquez (ESP/Derbi) 45.433, 6. Tomoyoshi Koyama (JPN/Aprilia) 49.685
Overall standings
1. Marc Marquez (ESP/Derbi) 132 points, 2. Pol Espargaro (ESP/Derbi) 131, 3. Nicolas Terol (ESP/Aprilia) 118, 4. Bradley Smith (GBR/Aprilia) 94, 5. Efren Vazquez (ESP/Derbi) 60
Moto2
1. Yuki Takahashi (JPN/Tech3), the 23 laps in 41:42.451, 2. Thomas Luthi (SUI/Moriwaki) at 5.037, 3. Julian Simon (ESP/Suter) 5.200, 4. Karel Abraham (CZE/FTR) 6.706, 5. Toni Elias (ESP/Moriwaki) 7.369, 6. Simone Corsi (ITA/Motobi) 7.414
Overall standings
1. Toni Elias (ESP/Moriwaki) 111 points, 2. Thomas Luthi (SUI/Moriwaki) 94, 3. Julian Simon (ESP/Suter) 77. 4. Shoya Tomizawa (JPN/Suter) 76, 5. Andrea Iannone (ITA/Speed Up) 70, 6. Simone Corsi (ITA/Motobi)