Organophosphates and pyrethroids are among the most common pesticides currently in use worldwide. Several pesticides have been reported to possess hormonal activities, and thus are classified as endocrine disruptors. The present study was planned to evaluate potential androgenic and antiandrogenic activities of the pesticides. The selected chemicals are three organophosphate pesticides including dichlorvos, parathion and trichlorphon, and two pyrethroid pesticides including permethrin and cypermethrin. We evaluated the pesticides for androgen receptor (AR)-mediated mechanisms using a human AR reporter gene assay in African monkey kidney cell line CV-1 transiently transfected with the constructed reporter gene plasmid pMMTV-CAT and the hAR expression plasmid AR/pcDNA3.1. We demonstrated that parathion showed significant inhibitory effects on the transcriptional activity induced by 1 nM of DHT with IC(50) value of (2.01+/-0.42) x 10(-7) M, though trichlorphon and dichlorvos lacked this activity. The two pyrethroid pesticides permethrin and cypermethrin exhibited lower activity than parathion with IC(50) value of (5.68+/-2.20) x 10(-5) and (6.80+/-2.30) x 10(-5) M, respectively. On the other hand, we failed to find AR-mediated androgenic activities of the tested chemicals. It is suggested that parathion possesses the highest activity, and permethrin and cypermethrin acted as poor antiandrogens. The present study provides insight into the mechanism of the pesticides.