Abstract Organochlorine pesticides (p,p′-DDT, p,p′-DDD, p,p′-DDE, aldrin, lindane, and heptachlor) were measured in muscle tissue of catfish ( Tachysurus thalassinus) during the dry and wet season. Catfish were collected from the South Patches of the Bay of Bengal during October–December 1997 and May–July 1998. Tissue residues were analyzed by using gas-chromatography (GC) in electron capture detector (ECD) mode and were verified by thin layer chromatography (TLC). The pesticide residues levels were found in order of Σ DDT>Heptachlor>Lindane>Aldrin. Higher levels of pesticide residues were found in all samples during dry season, as compared with the wet season, primarily due to elevated lipid content in fishes. A positive correlation and linear relationship was observed between the pesticide residues (ΣDDT and ΣOCs) and lipid content of fishes. However, the concentrations of pesticide residues in the muscle were found to be lower than the FAO/WHO [(1993) Food standards programme. Codex Alimentarius Commission, vol. 9 (4) pp. 149–158] recommended permissible limit for human consumption.