Abstract.Various formulations of six insecticides (a carbamate and five pyrethroids), were impregnated into bednets and curtains made from cotton, polyester, polyethylene or polypropylene fabric. For bioassays of insecticidal efficacy, femaleAnopheles gambiaemosquitoes were made to walk on the fabrics for 3 min and mortality was scored after 24 h. The main concentrations tested were: bendiocarb 400 mg/m2, cyfluthrin 30–50 mg/m2, deltamethrin 15–25 mg/m2, etofenprox 200 mg/m2, lambda‐cyhalothrin 5–15 mg/m2and permethrin 200–500 mg/m2. Field trials in Tanzania used experimental huts (fitted with verandah traps) entered by wild free‐flyingAnopheles gambiae, An. funestusandCulex quinquefasciatusmosquitoes.Results of testing the impregnated fabrics in experimental huts showed better personal protection provided by bednets than by curtains. Permethrincis:transisomer ratios 25:75 and 40:60 were equally effective, and the permethrin rate of 200 mg/m2performed as well as 500 mg/m2. Bioassay data emphasized the prolonged insecticidal efficacy of lambda‐cyhalothrin deposits, except on polyethylene netting. Most of the impregnated nets (including the ‘Olyset’ net with permethrin incorporated during manufacture of the polyethylene fibre) and an untreated intact net performed well in preventing bothAnophelesandCulexmosquitoes from feeding on people using them overnight in the experimental huts.Anophelesshowed high mortality rates in response to pyrethroid‐treated nets, but only bendiocarb treated curtains killed manyCulex.Holed nets treated with either cyfluthrin (5 EW formulation applied at the rate of 50 mg a.i./m2) or lambda‐cyhalothrin (2.5 CS formulation at 10 mg a.i./m2) performed well after 15 months of domestic use. Treatment with deltamethrin SC or lambda‐cyhalothrin CS at the very low rate of 3 mg/m2gave good results, including after w