Fifty-three young children with acute diarrhoea were included in a hospital-based, double-blind trial of loperamide at two dose levels (0.4 and 0.8 mg/kg/day), given with standard oral rehydration therapy versus placebo plus oral rehydration therapy. The differences in the overall recovery rate were significant (P less than 0.05), the fastest being in the group given 0.8 mg/kg and slowest in the placebo group. Comparison between weights on admission and weights by day 3 showed that more children in the loperamide groups gained weight than in the placebo group (P less than 0.05). No serious side effects of loperamide were observed. The drug was withdrawn in one child because of excessive lethargy and sleep. The results indicate that loperamide in the doses employed is safe and may be a useful adjunct to oral rehydration in certain children.