The Pampas is an extensive plain spreading over central and eastern Argentina and Uruguay, presenting a subtropical humid climate during the summer. It constitutes one of the best areas for agriculture worldwide. Numerical experiments with and without the Andes Cordillera (AC) were performed using the CPTEC general circulation model (spectral resolution T062 and 28 vertical sigma levels) to understand the influence of AC on Argentine-Uruguayan Pampas climate during the austral summer. An interesting result from the difference AC and no-AC experiments is the existence of a weak band of precipitation, consistent with vertical velocity at 500 hPa, extending from the southwest of Gran Chaco to the Atlantic Ocean through Uruguay and eastern Argentina Pampas. We have called this zone as Pampas Convection Zone (PAMCZ). This band is not as conspicuos on the summer climate of precipitation as the South Atlantic Convergence Zone (SACZ). Whereas the SACZ is a quasi-estationary rainfall system for 4 days or longer whose existence does not seem to depend on AC, PAMCZ seems to be just the preferred region for convection due the existence of AC. This result can help explain why frontal systems are enhanced over this area after crossing quickly the Patagonia region to the south, that is, why it is a frontogenetic zone. For similar reason, that area is favorable for formation of squall lines and mesoscale convective systems. Two important factors are responsible for the creation of PAMCZ: the first is the existence of low level southwesterly flow east of the AC over Patagonia region and the other is the existence of northeasterly flow east of the Peruvian and Bolivian Andes wich is responsible for water transport from tropical region to Chaco and Pampas regions, this feature being associated to the low level jet. Without the Andes Cordillera, the Pampas summer climate would be similar to the climate of a semiarid region.