Zinc supplementation has been consistently shown to reduce the incidence of childhood pneumonia, but its effect on the course of pneumonia when administered as an adjunct to antibiotic therapy is still unclear. Three trials published to date have shown mixed results, and a recent trial from India raises the possibility that zinc may be detrimental in some circumstances. Study sites and designs differ, particularly in the timing of zinc treatment and in determining recovery from pneumonia, which can explain the differences in study findings. Serum zinc concentrations are unreliable indicators of zinc status, particularly during acute infectious illnesses. Subgroup analyses, especially using serum zinc levels, must be cautioned against. Future studies are needed that are large enough to be sufficiently powered to accommodate larger treatment failure rates, an issue that ongoing trials will hopefully address.