The main features of the South America Monsoon system are simulated by the CPTEC/COLA AGCM in a climate ensemble simulation. Results of nine integrations with T62L28 model resolution for the period 1982-1991 are analysed in an ensemble mode and also considering daily results of the individual members. Low and upper levels wind fields in the summer season are typical and differ completelly of those of the winter. In the summer the Bolivian High and the Upper Atlantic Trough is well represented, as well as the position of the Atlantic subtropical High which affects the direction of the trade winds over the northeast brazilian coast. Extreme cases of precipitation anomalies over South America in the summer season are related to the behaviour of the main characteristics of the monsoon. An opposite relation occur between southeastern and southern Brazil during these extreme cases. The anomalies are associated with the direction of the low level flow from the Atlantic and Amazonia region, toward south, in the case of dry southeast and wet south, and toward southeast, in the case of dry south and wet southeast. It is seen, in these results, the opposite relation between the South Atlantic Convergence Zone (SACZ) and the Low Level Jet (LLJ) to the east of Andes. The extreme cases occur in ENSO episodes, suggesting a large scale influence on the South America Monsoon system. The overestimation of the SACZ by the model is also consistent with a reduced number of LLJ cases in the summer, when compared to the reanalyses results. Although the model, in ENSO years and in the climatology, represent well these features, in other years, the anomaly precipitation over central and southeastern Brazil is poorly simulated by the ensemble mean. The large dispersion among the members and the different behaviour of the synoptic systems over the region in each integration, give a low degree of predictability for this region, in contrast to the northeastern and the southern regions which have higher degree of predictability. Individual analysis of the member´s ensemble and the behaviour of the monsoon system in each case are performed to investigate the possibility of improvement in the seasonal prediction of the region.