The effect of Zn, as an adjunct to antibiotics, on the treatment of severe pneumonia in young children is still under debate; therefore, we performed a meta-analysis to evaluate the therapeutic role of Zn for severe pneumonia in children younger than 5 years. PubMed, Cochrane library and Embase databases were systematically searched from inception until October 2015 for randomised-controlled trials (RCT) that assessed the effect of Zn as an adjunct to antibiotics for severe pneumonia. Random-effects model was used for calculating the pooled estimates, and intention-to-treat principle was also applied. Nine RCT involving 2926 children were included. Overall, the pooled results showed that adjunct treatment with Zn failed to reduce the time to recovery from severe pneumonia (hazard ratios (HR) = 1·04; 95 % CI 0·90, 1·19; I 2 = 39 %; P = 0·58), hospital length of stay (HR = 1·04; 95 % CI 0·83, 1·33; I 2 = 57 %; P = 0·74), treatment failure (relative risk (RR) = 0·95; 95 % CI 0·79, 1·14; I 2 = 20 %; P = 0·58) or change of antibiotics (RR = 1·07; 95 % CI 0·79, 1·45; I 2 = 44 %; P = 0·67). In addition, continuous outcomes were consistent while meta-analysed with standard mean difference, and all outcomes remained stable in intention-to-treat analysis. No significant differences were observed in the two groups between death rate, adverse events or recovery times of severe pneumonia indicators. Our results suggested that adjunct treatment with Zn failed to benefit young children in the treatment of severe pneumonia. Considering the clinical heterogeneity, baseline characteristics of children, definition of severe pneumonia and Zn supplement way should be taken into consideration in future research. This study was registered at PRESPERO as CRD42015019798.Key words: Children: Meta-analyses: Severe pneumonia: ZincPneumonia is a leading disease and cause of death in children under 5 years in developing countries (1) . It is reported that 14·9 % of 6·3 million deaths of children <5 years old were caused by pneumonia worldwide (2) . With advances in medicine, economy and society, pneumonia with diarrhoea and measles was responsible for half of the reduction in mortality of children under 5 years from 2000 to 2013 (2) . Although great progress was achieved, only a few countries could reach the goal of Millennium Development Goal 4 to reduce under 5 child mortality by two-thirds between 1990 and 2015, and pneumonia is still the leading cause of child mortality (3) . Therefore, intensive effort should be made in the research of pneumonia.Under-nutrition has been reported to be strongly associated with impaired immune response, (4) and it has been proven to be responsible for greater severity of pneumonia, prolonged course of disease and increased mortality of pneumonia (5) .Zn, as an important micro-element, has an essential role in cellular growth and immune defence, and its deficiency is associated with significant increased susceptibility to various infection pathogens (6)(7)(8) . In a randomised-controlled trial (RCT...