The prescnt srudf investtsates &e effecs induccd b1' sildenafil (0.004 and 0.(X)8 mg/gm' p.o.) on copulatory- beberior of malc rers. performed on serue- inactive male rat model against sexually highl;- receptive femaler -{L.o. h reri.$s currart eridencr rcgilditrC its central sexual effect on decreased desire (libido) arousal difficuhits erd orgasm- Parametcn of sexuil behavior were assessed including mount' intromission, and ejrcularion htencies ud frequeacitt Als*. serum follicle-stimulating hormoqe (FSH), luteinizino hormone (LH) lnd prolactil lereb r*-cre chccked ia serually inacth-e rats in comparison to control end normel intrct rrrs The d.rte obteined shor that sildeuafil modifies both sexual arousal and ejaculator-v mcchanisms of copulation It epptan thrt althougi it induced a facilitatory effect on ejacularion of all rets- the hncring of ejaculetor.v thrcshold was achieved by means of a reduction of mount frequenc.v and intromirsion frequencf in both scruallf inactiv-e rats and those rvith normal serual actiriS'. Sildenelil iacrustd scruel rrous:|. itr both seruallf inactive and rats with normal serual acthir;-. It was fouod tbt. i! scrualll- inctive nt modcl there trs a statisticall-r- significant decrease in mount, htromission end ejecalation htencies (P4.05 ; P4.05 and p