Satellite ocean colour data from the Sea-Viewing Wide Field-of-View Sensor are analyzed to monitor the space-time variability of the Plata river plume over the continental shelf and slope. SeaWiFS Chlorophyll-a (CSAT) product is used to understand the nature of changes in the colour of waters and how this relates to variations in wind direction and river outflow. We use a 5-year data set (1998-2002) of Global Area Coverage monthly mean composites. The analysis of CSAT data reveals strong seasonal variability over the continental shelf with maximum northeastward penetrations in the austral winter (June to August). The plume may reach ~27S, about 1000 km northeast of the Plata estuary. In summer the plume is confined to south of 32&deg;S and the Plata waters are frequently exported to the open ocean through the Brazil/Malvinas Confluence. This seasonal shift is similar to the variation of surface salinity observed in historical hydrographic data and is presumably associated to the variable influence of the along-shore wind stress. Interannually, 2002 showed the maximum northeastward penetration and the strongest anomalies (6mg/m³). From late 1999 to early 2000, a strong negative CSAT anomaly (<6mg/m³) within the estuary could be linked to a period of very low Plata outflow (<12,000m³/seg). Results suggest that CSAT geophysical product is a good indicator of the presence of the Plata diluted waters. Other Case II ocean colour products are being explored (CDOM)