The present study was carried out from May 1991 to April 1993 to evaluate the trawl fishery in the Portugal Bay area of the northwestern coastal waters of Sri Lanka. The main craft types engaged in the trawl fishery are 11 t crafts and 3.5 t wooden boats. There were 17, 11 t trawlers and around 35, 3.5 t wooden boats. The estimated average catch rates for 3.5 t and 11 t crafts for the study period were 22.7 kg/haul and 73.4 kg/haul respectively. The target species of the trawl fishery by both craft types is prawns. Prawns alone contribute 10% and the 32% of the total catch of 11 t and 3.5 t crafts that operate in the Portugal Bay area. However, the by-catch also contributes to the economy of these operations. The major finfish varieties caught are the fish belonging to the families Leiognathidae, Ariidae and Rajidae. Among these, Leiognathids seem to constitute a major portion contributing around 34% of the by-catch. Leiognathus brevirostris constitutes about 44% of the catch of the ponyfish. The estimated annual yield from the trawl fishery obtained for the periods 1991-1992 and 1992-1993 were 662 MT and 474 MT respectively. Seasonality in the trawl fishery was observed with a peak period from September to March of each year. The environmental factors such as rainfall and phase of the moon have not affected the catch rates significantly.