Small cetaceans and some great whales become entangled and die in gillnets in a variety of fisheries in the northeastern Indtan Ocean. Information on operational details, present status and future plans for development of fisheries was compiled from published literature, widely-distributed questionnaires the author’s own research. The study concentrated on fisheries for 14 fish species or groups of species (seerfish, tunas, pomfrets, sharks, skates and rays, catfish, polynemids, oil sardines, mackerels, lesser sardines, whitebait, hilsas, riverine catfish and prawns) and cetaceans entangled and killed during their operations. In general, documentation of the extent of cetacean mortality is poor but sufficient to suggest that mortality is high in at least some fisheries (e.g. driftnet fisheries) and in some countries (e.g. Sri Lanka and India). Apparently low levels of mortality noted for Bangladesh and Burma may be due to low fishing effort. It is suspected that the primarily hook-and-line methods employed in the Maldives minimise the chance of serious levels of cetacean entanglement. Virtually all cetacean species known to inhabit the areas of operation become entangled at some time, and rates of mortality for some species in some areas appear high. This fishery-related mortality occurs at a time when national programmes are encouraging further expansion and development of fisheries to feed burgeoning human populations. Recommendations are made to increase programmes of cetacean research, public awareness and monitoring of cetacean mortality and its impact on cetacean populations.