The composition of the particulate matter at two stations in the Vellar estuary was determined and the relationships between organic carbon, chlorophyll a and particulate phosphorus were examined. The regression of chlorophyll on carbon possibly indicated the presence of an appreciable quantity of carbon contributed by detrital material. Chlorophyll a verses phosphorus showed a better relationship than carbon versus phosphorus. The particulate matter of the estuary seem to be largely composed of detritus