Fatty acid composition of the body oils of 12 marine fish species of the Bay of Bengal was determined by gas-liquid chromatography. Two fishes from freshwater were also studied for comparison. Saturated fatty acids composed the largest proportion, ranging from 38 to (59 %) of total fatty acids in the marine and from 40 to (46 %) in the freshwater fish. The monoenes and the (\omega-3) polyunsaturates were close to each other in composing the second and the third largest fractions of the marine fish fatty acids, respectively. The monoenes ranged from 9.9 to (38 %) and (\omega-3) fatty acids ranged between 8.9 and (35 %). The (\omega-3) fatty acids contributed much less, (7.0-12 %), in the freshwater fish. The (\omega)-6 polyunsaturates were the smallest group, composing (2.5-9.2 %) in both marine and freshwater fish. Of the saturates, (16: 0) was the major fatty acid. followed by 18:0. C18: 1 and 16:1 were the dominant monoenes. While 20:4 was the only major (\omega-6) fatty acid, 20:5 and 22:6 were prominent (\omega)-3 fatty acids. In addition, another very long-chain fatty acid, likely 24:6, (\omega)-3, was dominantly present in 7 of the 12 marine and none of the freshwater fish. %1993 Academic Press. Inc.