Meta-analyses have shown that zinc supplementation is useful for diarrhea and pneumonia prevention in developing countries [12, 13]. It has been extensively shown that zinc is an important adjunct to diarrhea treatment [13]. With regard to pneumonia, only three recent studies have reported the use of zinc as an adjunct to antimicrobial treatment for pneumonia in children. A clinical study performed in Kolkata, India, in children with acute lower respiratory infection who were given zinc supplements, demonstrated a significant reduction in the duration of fever and very ill status only in boys, but not in girls [14]. The weaknesses of this trial included the small sample size and the fact that the observed beneficial effect was based on a subgroup analysis. Another study performed in Vellore, India, in a larger group of children younger than 2 years of age, demonstrated that zinc, as an adjunct to antimicrobial treatment, did not have an overall effect on the duration of hospitalization or clinical signs associated with pneumonia [15]. In addition, Bose et al reported that the use of zinc was associated with an increased duration of clinical signs of pneumonia. These different findings could be explained by the dissimilarities between both geographical locations and mean basal plasma zinc concentrations in these studies (Kolkata: 63 µg/dl vs. Vellore: 72 µg/dl). Nevertheless, a clinical trial performed in Bangladesh reported that the use of zinc as an adjunct to the treatment of severe pneumonia in children reduced the duration of clinical manifestations of the disease including chest indrawing, tachypnea, hypoxia, and length of hospitalization [16]. This study had a sample size similar to the trial in Vellore [15] and thus had adequate power. In summary, there are conflicting results on the effect of zinc given during a severe pneumonia episode in young children. Pneumonia etiology is one factor that has been extensively discussed as a possible mechanism to explain the controversial findings of these studies. Bose et al. suggested that the increased duration of pneumonia signs during zinc supplementation might be due to different etiologies of pneumonia [15]. Brooks et al. speculated that the observed reductions in pneumonia duration might be explained by zinc's role in the acute phase response to pathogens [16]. However, at present there is no evidence showing that zinc supplementation has an etiology-dependent effect on the clinical evolution of pneumonia. In a recent editorial, Hambidge also suggested that the controversial findings from these three studies could be due to the basal zinc status of the intervention groups, associated pneumonia pathogens, and age of the enrolled children [17].