OBJECTIVES: To determine the role of zinc supplementation in children with watery diarrhoea. The objective was to compare the mean change in frequency of stool with zinc supplementation versus placebo in children with acute diarrhoea in addition to standard treatment. METHOD: It was a randomized controlled trial conducted in Paediatric Department, Punjab Rangers Teaching Hospital, Lahore over 6 months. 68 children of both genders aged under 5 years who presented with acute diarrhoea were sub-divided into two equal groups; Group -A received oral zinc with standard management while those in Group-B received standard management alone. Frequency of stools was recorded after 72 hours, mean change calculated and then compared between the groups. RESULTS: Mean duration of acute diarrhoea was 3.81±1.56 days. Both the study groups were comparable in terms of mean frequency of stools at presentation (7.71±2.76 vs. 7.79±2.67; p-value=0.894). However, after 72 hours, the mean frequency of stools was significantly lower in children receiving additional zinc supplementation as compared to placebo (3.94±2.84 vs. 5.50±2.77; p-value=0.025). The mean change in the frequency of stools was significantly higher in the zinc group as compared to placebo group (3.76±0.89 vs. 2.29±0.63; p-value<0.001). CONCLUSION: In this study, zinc supplementation was found superior to conventional management of children presenting with acute diarrhoea evident from considerably greater reduction in the mean frequency of stools. The low cost, wide-spread availability and ease of administration advocate the preferred use of zinc in the management of such patients.