Abstract An emulsion containing 0·018 per cent pyrethrins and 0·036 per cent piperonyl butoxide, applied to smoke-dried freshwater fish in Zambia, prevented infestation by Dermestes ater and D. maculatus (partly by repelling adults) but became ineffective 8–12 weeks after application. An emulsion containing 0·125 per cent malathion gave good control for 8 weeks, but left up to 43 ppm active ingredient in Tilapia spp. 8 weeks after treatment, and fish became littered with dead dermestid adults. Pyrethrum dust gave relatively poor protection and a silica-based dust was ineffective. Brining to give 8–10 per cent salt in the final product did not prevent infestation although it reduced damage due to dermestid larvae. Fish treated with pyrethrins emulsion or brine were superior in condition compared with untreated fish after 12 weeks storage. A taste panel preferred brined fish to untreated fish but could not distinguish brined from pyrethrins-treated fish. Bacterial counts indicated that both brined and pyrethrins-treated fish were virtually sterile after 12 weeks storage, but bacterial loads on control fish were also low, 6600–60,000/cm 2. The pyrethrins emulsion treatment was shown to be economically very attractive, and was considered to be most appropriate in Zambia.