An open multicentre trial was undertaken in 8 countries to assess the efficacy and tolerance of short course treatment regimens of tinidazole Trichomoniasis: of 859 patients with trichomonal vaginitis given a 2g single dose of tinidazole 717 (95.2%) were cured. Side-effects occurred in 82 patients (9.5%) and in 12 were regarded as severe. Giardiasis: of 74 children with symptomatic giardiasis given tinidazole in a single dose of approximately 50 mg/kg body weight, 65 (88%) were parasitologically and symptomatically cured. 2 (2.7%) complained of side-effects, none of which was severe. Intestinal amoebiasis: of 502 patients, comprising 458 adults and 44 children, with symptomatic intestinal amoebiasis who received tinidazole as a single daily dose on 2 to 3 consecutive days, 477 (95%) were parasitologically cured with complete or marked improvement in symptoms. Side-effects occurred in 50 patients (10%) and in 11 were regarded as severe. Amoebic liver abscess: 82 patients were given tinidazole in single doses of 2g on 3 consecutive days. The response was rated as excellent in 60 and good in 17 (overall cure 93.9%). Side-effects occurred in 9 patients (10.9) and in 2 were regarded as severe. These findings confirm the efficacy and tolerance of short regimens of tinidazole given in single daily doses.