Data from the Coastal Zone Color Scanner (CZCS) was used to study the abundance and variability of chlorophyll a in the southeastern Indian Ocean, an interesting region because it includes the Indonesian through-flow and the anomalous Leeuwin Current. This study is the first to interpret the CZCS observations in terms of the spatial-temporal variability of this large area. The period of data (1979 to 1986) covered the full cycle (pre, during and post) of a major El Nino event, which has yet to be done by the more recent ocean color sensors. The highest seasonal mean chlorophyll a concentrations along the NorthWest Shelf of Australia occurred in Summer (January-March) and in coastal areas off south-western Australia in Autumn (April-June). Concentrations in the offshore oceanic regions were mostly poor. Exceptions to this occurred in proximity to the adjacent Indonesian islands and directly south of Albany (possibly due to northwards flow of subantarctic nutrient-rich waters). A considerable interannual variation was also noted, with the highest mean chlorophyll a concentrations occurring in 1981, 1982 and 1983.