Data on the distribution of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) in relation to phytoplankton abundance in different oceanic environments is important to understand the biogeochemistry of DMS, which plays an important role in the radiation balance of the earth. During the summer monsoon of 2001 measurements were made for DMS and DMSP t (total DMSP) together with related biological parameters in the Bay of Bengal. Both DMS and DMSP t were restricted to the upper 40m of the water column. Diatoms accounted for more than 95% of the phytoplankton and were the major contributors to the DMS and DMSP t pool. The mean concentration of DMS in the upper 40m was observed to be around 1.8±1.9nM in the study area, while DMSP t concentrations varied between 0.7nM and 40.2nM with a mean of 10.4±8.2nM. The observed lower DMSP t in the northern Bay in spite of higher mean primary productivity, chlorophyll a and phytoplankton cell counts seemed to result from grazing. Though salinity divides the Bay into different biogeochemical provinces there is no relation between salinity and DMS or DMSP t . On the other hand DMS was linearly related to chlorophyll a:phaeopigments ratio. The results suggest the need for deeper insight into the role of diatoms in the biogeochemical cycling of DMS.