The results of an analysis of rainfall variability over South America and the South Atlantic region (15N-40S, 80W-20W) at interannual timescales are presented. The work is based on monthly mean satellite OLR from 1974-1999. Daily OLR observations are low pass filtered to remove intraseasonal variability, which may otherwise alias onto monthly timescales and thus influence interannual variability. EOF analysis of monthly mean filtered OLR over the DJF season was conducted and three leading EOFs retained. Composite and correlation analysis using NCEP reanalysis data and observed SSTs yield insight into the mechanisms of variability associated with these EOF patterns. EOF1 has positive (negative) loadings over northern South America (subtropical plains and Atlantic) and is strongly related to ENSO. EOF2 represents interannual variability in the South Atlantic Convergence Zone, and is associated with SST anomalies in the subtropical western Atlantic. EOF5 is indicative of meridional variability in the position of the ITCZ in equatorial regions. With the linear influence of ENSO removed from the data there is evidence of a relationship with the NAO.