A novel series of 5-nitroimidazole-piperazines (4a-j) and 5nitrothiazole-piperazine (7a-j) have been prepared in good yields. The antigiardial and antitrichomonal activities of these new compounds were evaluated. Majority of the compounds was found to be more active against Giardia lamblia as compared to metronidazole at 24 hours of incubation. After 48 hours of incubation, compounds 4b, 4f, 7c and 7j showed better activity against G. lamblia with IC 50 of 15.3, 11.4, 5.9, 13.5 mM respectively compared to metronidazole (17.4 mM). Compounds 4a-j and 7a-j exhibited anti-parasitic activity against T. vaginalis with IC 50 ranging from 16.4-88.7 mM and 1.2-86.7 mM at 24 hours and 48 hours of incubation respectively. Compounds 4c and 7e were 15 times more potent than the standard drug, metronidazole.[a] Dr.