In a comparative trial, 165 Cuban children with confirmed giardiasis were randomized to receive albendazole (400 mg/day for 5 days), chloroquine (10 mg/kg twice daily for 5 days) or tinidazole (50 mg/kg, as a single dose). Parasitological follow-up was based on faecal samples collected 7 and 10 days after the completion of treatment. The tinidazole and chloroquine appeared equally effective (P > 0.05), curing 91% and 86% of the children treated, respectively, and significantly better (P < 0.01) than the albendazole, which only cured 62% of the children given it. All three drugs were well accepted and tolerated, with only mild, transient and self-limiting side-effects reported. Chloroquine appears to be a good alternative to tinidazole for the treatment of paediatric patients with giardiasis.