Therapeutic effects of metronidazole (Flagyl), tinidazole (Tricolam 500) and chlorhydrate of quinacrine in a study of 106 children with symptomatic giardiasis are compared. To evaluate results, cure percentage, efficacy and presence of secondary effects were quantified. Tinidazole was demonstrated most effective drug (96% effective) when compared with quinacrine (83.3% effective) and metronidazole (70.2%) (p less than 0.05). Authors recommend following regime: tinidazole 50-75 mg/kg divided in 2-3 doses, one day; chlorhydrate of quinacrine 6 mg/kg/day divided in 3 doses, five days; metronidazole 15-20 mg/kg/day divided in 3 doses, seven to ten days.