Primary productivity and related aspects in the Vizhinjam Bay and adjacent open sea were investigated from April 1983 to March 1984. The rate of production was estimated by determining O by the light and dark bottle method. The gross production in Vizhinjam Bay ranged from 114 to 672 mg C/m³/day and in the open sea station it varied from 185 to 739 mgC/m³/day. The range in the net production was from 32 to 429 mg C/m³/day in the Bay and from 114 to 411 mg C/m³/day in the open sea station. High values of phosphate were recorded in September and October in the Bay and during August November in the open sea. The nitrite and nitrate values were low when compared to those reported earlier from Vizhinjam Bay. The monthly variations in surface production were not significantly related to either temperature or salinity. The correlation between primary production and nutrient concentration was discussed.