Propolis, a honey bee product, gained popularity in alternative medicine. Its prophylactic and therapeutic effects were experimentally evaluated. One hundred and fifty immunocompetent mice were orally infected by 5 x 10(5) axenically cultivated Giardia lamblia trophozoites. The trophozoite count in intestine, interferon-gamma serum level, histopathological examination of duodenal and jejunal sections were assessed for evaluation of propolis and metronidazole (MTZ) effect after 6 & 12 days post infection (p.i). Also, T-lymphocyte profile in blood was investigated 12 days p.i using flow cytometry (FCM). Propolis as prophylaxis showed a significant decrease in intensity of infection, together with a significant increase in IF-gamma serum level and increase in CD4+: CD8+T-cell ratio. In treatment it gave a highly significant decrease in trophozoite count than that obtained by MTZ 6 days after infection but the efficacy was almost equal after 12 days. The mice treated with propolis alone showed a reversed CD4+: CD8+ T-lymphocyte ratio, such strong immune enhancing effect resulted in an undesirable increase in inflammatory response at intestinal level. The combined therapy showed a stronger efficacy in reducing the parasite count than that gained by each drug alone. Their combined use caused an immunological balance as shown by the T-lymphocyte profile that saved the intestinal homeostasis and histological architecture.