This study tested the efficacy of permethrin-impregnated mattress liners in reducing house dust mites in the homes of volunteers with no previous recorded history of asthma, atopic eczema, or perennial rhinitis. The field trial using permethrin-impregnated (450 mg/m2 of pure permethrin in polyester netting weighing 35 g/m2) mattress liners (n = 9) was conducted for 27 mo. The permethrin-impregnated bedding significantly reduced house dust mites in mattresses for at least 27 mo. Allergen concentrations were significantly lowered at 15-mo postintervention. No adverse side-effects were reported. This is a promising development in house dust mite control.