Medicinal plant extracts from 27 plant species in 20 families were tested for their larvicidal activity against house fly, Musca domestica (L.). Responses varied with plant material and concentration. Among plant species tested, Phryma leptostachya var. asiatica showed 100% larvicidal activity against M. domestica at 10 mg/g concentration. Larvicidal activities of Atractylodes japonica, Saussurea lappa, Asiasarum sieboldi, and Gleditsia japonica var. koraiensis were 89.3, 85.3, 93.3 and 96.6% at 10 mg/g concentration, respectively. Extracts of Prunus persica, Curcuma longa and Paeonia moutan produced moderate activity. Larvicidal activity of other plant extracts was less than 50%. Among test plant species, Phryma leptostachya var. asiatica showed the most potent larvicidal activity. The active constituent of P. leptostachya var. asiatica roots was identified as the leptostachyol acetate by spectroscopic analysis. The LC50valuesofleptostachyolacetateagainstM. domestica larvae was 0.039 mg/g. Naturally occurring medicinal plant extracts and Phryma leptostachya var. asiatica root–derived compounds merit further study as potential house fly larval control agents or lead compounds.