The loss of permethrin from impregnated uniforms due to repeated washings was studied by chromatographic estimation of the residues. The mean (± SEmean) percentage losses of permethrin after one to five washings were 16.7 ± 2.3, 22.5 ± 3, 29.6 ± 2.9, 40.2 ± 2 and 52.2 ± 2.4, respectively. The reduction in contact toxicity against mosquitoes after each washing was studied by World Health Organization tube and cone bioassays against Aedes albopictus mosquitoes. The median knockdown time for 5-min exposure to the treated uniforms increased from 5.9 to 71.8 min after five washings. Mosquito mortality 24 h post-exposure in cone bioassays was <80 % after the fifth washing, indicating the loss of efficacy. The uniforms need to be retreated after five washings so as to ensure adequate protection against disease vectors. The washing water should be properly disposed off to prevent environmental contamination and toxicity to aquatic organisms. Methods for treatment of military uniforms, which ensure high resistance to washing, need to be adopted so as to avoid frequent re-impregnations with permethrin.