AIMS. Treating uniforms with permethrin is registered as a useful technique to protect soldiers against biting. This study evaluates the effect of washing on endurance and persistency of permethrin and its contact toxicity in treated uniforms.

METHODS. This is an intervention experimental study which done during 2003-2005 in two laboratories of Tehran university of medical sciences. Six different kind army uniforms fabrics, which commonly used in Iran military, impregnated with permethrin at 0.125 mg (AI)/cm² (EC %10). Amount of permethrin residue was determined by High Performance Thin Layer Chromatography (HPTLC) technique using TLC-Scanner 3. Treated cloth patches were used in bioassay test against Anopheles stephensi .

RESULTS. Washing uniforms result in meaningful decreasing of permethrin amount in impregnated clothes patches and also their insecticide ability. Hand washing of uniforms decreased 25-35% of residual permethrin and machine washing of them decreased 50-65% of residual permethrin amount.

CONCLUSION. Washing the clothes is something inevitable which can reduce insecticide ability . Impregnation with normal formulation is appropriate for short-time purposes and for long-time purposes polymer-coating formulation or other durable long lasting formulations must be used.