Ever since the pioneering work of Velasco and Fritsch (1987), it has been known that rainfall over South America often comes in large organized mesoscale convective systems (MCSs). The Tropical Rain Measuring Mission (TRMM) was launched in late 1997, and provides the best opportunity for making quantitative estimates of rainfall over the entire continent (north of 36 S) and partitioning that rainfall into different types of cloud and precipitation systems. A striking result is that subtropical South America (southern Brazil, Uruguay, northeastern Argentina and Paraguay) has the highest contribution (greater than 80 percent) of rain from MCSs to the total rainfall of any location on earth between 36 N and 36 S. The TRMM rainfall estimates are compared with those from dense rain gauge networks on the ground. This presentation reports on some of the consequences of rainfall from MCSs in different regions and regimes of precipitation in the continent. It also reports how some discrepancies found in the algorithms can be used to assess potential biases in various remote sensing rainfall estimates.