Professor Robert E. Black’s long-standing works on the importance of childhood nutrition significantly contribute to the wide application of zinc supplementation. His earlier studies in Bangladesh and India demonstrated that daily zinc supplementation during diarrheal episodes significantly reduced the severity of diarrhea. Similar situation occurs in pneumonia cases. He also described the diarrhea-nutrition cycle in which episodes of diarrhea lead to malnutrition and deficiency of trace elements, and in turn further augment the incidence and severity of diarrhea. The World Health Organization and UNICEF currently recommend that all childhood diarrhea cases should be treated with zinc supplement as well as oral rehydration. The program has been implemented in more than 40 countries around the world.