Seasonal and interannual variability in satellite-derived estimates of near-surface chlorophyll-a concentrations were examined in the four regions off the southwest coast of India from 1998-2003. Wind-induced upwelling predominates in late spring and summer, coinciding with the maximum in solar radiation, leading to increased accumulations of phytoplankton biomass. Chlorophyll concentrations varied from 2 to 10 mg/m3 and were generally lower in January-April and maximal in May-September. Chlorophyll concentrations along the coast followed a similar seasonal pattern (ranging from 0.5 to 4 mg/m3); however, concentrations were always greater on the Trivendrum and Cochin coast compared to the Calicut and Mangalore coast. The southwest coast is often cloud covered; data density maps provide an index of confidence in the 'regional' applicability of the summary statistics. One consequence of the 1997-1998 El Nino appears to be a reduction in chlorophyll concentration off Trivendrum and Cochin in 1998. An increased frequency of El Nino events may lead to a reduction in offshore carbon in this dynamic upwelling region. Six-month median chlorophyll concentrations were maximal in 2002 off Trivendrum and Cochin.