Despite tropical estuarine systems representing important sites for active biogeochemical processes, studies on dimethyl sulphide (DMS) in these systems are sparse. Here we report on DMS and dimethylsulphoniopropionate (DMSP) variability in relation to physicochemical and biological parameters for a period of 14 months in a tropical estuarine environment. DMS and DMSP showed high temporal variations with maximal concentrations during the southwest monsoon coinciding with a dinoflagellate bloom. Dinoflagellates appear to be the major contributors to the DMSP pool. Average DMS and DMSP concentrations (surface and bottom) suggested that much of the DMSP produced is converted to forms other than DMS. Surface DMS varied between 0.3 and 15.4 nmol dm super(-3) while DMSP ranged from 0.8 to 419.5 nmol dm super(-3). The DMS flux was 0.03-1.9 M m super(-2) d super(-1) (average=0.6 M m supeer(-2) d super(-1)) during the study period, that concurs well with the values reported for temperate