The aim of the study was to test new treatment protocols for giardiasis, which are less toxic, cheaper, and easier to use than the conventional treatment. 48 children who had been diagnosed as having giardiasis in a health-screening program involving 2 schools, were randomized to receive four different treatment protocols. The children were split into 4 treatment groups: I, mebendazole 100 mg t.i.d. for 1 day; II, mebendazole 100 mg t.i.d. for 7 days; III, metronidazole 15 mg/kg as one dose for 7 days; and IV, ornidazole 40 mg/kg as a single dose. The results were evaluated by microscopic examination of stools. The responses to the treatments revealed that the effectiveness of ornidazole was 100%, metronidazole 92.9%, mebendazole for 7 days 58.3%, and mebendazole for 1 day 41.7%. Minor side-effects were seen in only 3 children receiving ornidazole: 1 had urticaria, while the other 2 suffered from vertigo and nausea. The results of this study show that ornidazole as a single dose can be used as an alternative protocol for treating giardiasis. Further studies should be done to determine the safest effective total single dose.