The study was a double-blind, controlled, randomized by episode in two sub-district rural areas ± 200 km from Jakarta, in which 1,185 children under three years of age were assigned to receive 4-5 mg element zinc/kg bw/day as a daily dose in two divided doses for the consecutive days during diarrhea Children were visited at their home every week for 12 months and they also underwent oral rehydration therapy. After 12 months observation there were 2, 410 episodes, 131 were excluded due to lack of information.Among children of zinc supplementation group there was 11% reduction (95% confidence interval, 3 to 18%) in the risk of continued diarrhea. In children with watery diarrhea there was a decreased of 12% (95% confidence interval, 3 to 21%) in the number of days in the zinc supplementation group. The reduction in the likelihood of diarrheal duration was 18% (95% confidence interval, 4 to 43%) in children who were given antibiotics before enrollment. Among children who had 3 episodes during 12 months observations there was a greater reduction in diarrheal duration (RR. in the zinc supplementation group = 0.79; 95% confidence interval, 0.64 - 0.97). Zinc supplementation in children with stunted growth was associated with 8% reduction of the risk of continued diarrhea, but statistically not significant (95% confidence interval, -9 to 21%). Children in zinc group had a lower proportion of persistent diarrhea (z 14 days) than control group zinc supplementation resulted in a 44% (95% confidence interval, 2 - 70%) reduction in the incidence of persistent diarrhea.These findings suggest that zinc supplementation in children with acute diarrhea significantly reduced the duration of diarrhea and the risk of persistent diarrhea. Zinc supplementation may have a significant effect on childhood diarrhea-related mortality.