A randomized controlled trial, 113 school children with Giardia intestinalis infection were treated with albendazole or tinidazole. Albendazole 400 mg once a day x 3 days and tinidazole 50 mg/kg single dose were given orally to 62 and 51 children, respectively. Parasitological cure was documented when there were > or = 2 times negative stool examination for G. intestinalis at 1-2 weeks after therapy. Thirty-one of 62 (50%) children treated with albendazole and 49 of 51 (96.1%) children treated with tinidazole had parasitological cure (p < 0.001). No major side effects were observed except one case in tinidazole group had severe headache for 30 hours. Albendazole appears to be safe and produced a moderate cure rate for G. intestinalis infection when a 3 day anthelmintic regimen is given.