A significantly lower incidence and prevalence of diarrhea has been observed in zinc supplemented developing country children in several placebo-controlled trials. The effect of routine zinc supplementation on lower respiratory tract infection is still unclear. We, therefore, evaluated the impact of daily zinc supplementation in a representative sample of children aged 6 to 30 months enrolled from a New Delhi slum area, with a sample size sufficient to determine the impact on the incidence of severe diarrhea and acute lower respiratory infection.