Background: Zinc deficiency is associated with impaired immune function and an increased risk of infection. Supplementation can decrease the incidence of diarrhoea and pneumonia in children in resource-poor countries. However, in children with HIV- 1 infection, the safety of zinc supplementation is uncertain. We aimed to assess the role of zinc in HIV- 1 replication before mass zinc supplementation is recommended in regions of high HIV- 1 prevalence. Methods: We did a randomised double-blind placebo-controlled equivalence trial of zinc supplementation at Grey’s Hospital in Pietermaritzburg, South Africa. 96 children with HIV- 1 infection were randomly assigned to receive 10 mg of elemental zinc as sulphate or placebo daily for 6 months. Baseline measurements of plasma HIV- 1 viral load and the percentage of CD4+ T lymphocytes were established at two study visits before randomisation, and measurements were repeated 3, 6, and 9 months after the start of supplementation. The primary outcome measure was plasma HIV- 1 viral load. Analysis was per protocol. Findings: The mean log10 HIV- 1 viral load was 5.4 (SD 0.61) for the placebo group and 5.4 (SD 0.66) for the zinc-supplemented group 6 months after supplementation began (difference 0.0002, 95% CI - 0.27 to 0.27). 3 months after supplementation ended, the corresponding values were 5.5 (SD 0.77) and 5.4 (SD 0.61), a difference of 0.05 (- 0.24 to 0.35). The mean percentage of CD4+ T lymphocytes and median haemoglobin concentrations were also similar between the two groups after zinc supplementation. Two deaths occurred in the zinc supplementation group and seven in the placebo group (p=0.1). Children given zinc supplementation were less likely to get watery diarrhoea than those given placebo. Watery diarrhoea was diagnosed at 30 (7.4% ) of 407 clinic visits in the zinc-supplemented group versus 65 (14.5% ) of 447 visits in the placebo group (p=0.001). Interpretation. Zinc supplementation of HIV- 1- infected children does not result in an increase in plasma HIV- 1 viral load and could reduce morbidity caused by diarrhoea. Relevance to Practice: Programmes to enhance zinc intake in deficient populations with a high prevalence of HIV- 1 infection can be implemented without concern for adverse effects on HIV- 1 replication. In view of the reductions in diarrhoea and pneumonia morbidity, zinc supplementation should be used as adjunct therapy for children with HIV- 1 infection. Background: Zinc deficiency is associated with impaired immune function and an increased risk of infection. Supplementation can decrease the incidence of diarrhea and pneumonia in children in resource-poor countries. However, in children with HIV-1 infection, the safety of zinc supplementation is uncertain. We aimed to assess the role of zinc in HIV-1 replication before mass zinc supplementation is recommended in regions of high HIV-1 prevalence. Methods: We did a randomized double-blind placebo-controlled equivalence trial of zinc supplementation at Gray’s Hospital in Pietermaritzburg, South Africa. 96 children with HIV-1 infection were randomly assigned to receive 10 mg of elemental zinc as sulphate or placebo daily for 6 months. Baseline measurements of plasma HIV-1 viral load and the percentage of CD4 + T lymphocytes were established at two study visits before randomisation, and measurements were repeated 3, 6, and 9 months after the start of supplementation. The primary outco Findings: The mean log10 HIV-1 viral load was 5.4 (SD 0.61) for the placebo group and 5.4 (SD 0.66) for the zinc-supplemented group 6 months after supplementation began (difference 0.0002, 95% CI - 0.27 to 0.27). 3 months after supplementation ended, the corresponding values ​​were 5.5 (SD 0.77) and 5.4 (SD 0.61), a difference of 0.05 percentage of CD4 + T lymphocytes and median hemoglobin concentrations were also similar between the two groups after zinc supplementation. Two deaths occurred in the zinc supplementation group and seven in the placebo group (p = 0.1). Children given zinc supplementation were less likely to get watery Watery diarrhea was diagnosed at 30 (7.4%) of 407 clinic visits in the zinc-supplemented group versus 65 (14.5%) of 447 visits in the placebo group (p = 0.001). Interpretation. Zinc supplementation of HIV- 1- infected children doesnot result in an increase in plasma HIV-1 viral load and could reduce morbidity caused by diarrhea by using a high prevalence of HIV-1 infection can be implemented without concern for adverse effects on HIV-1 replication. In view of the reductions in diarrhea and pneumonia morbidity, zinc supplementation should be used as adjunct therapy for children with HIV-1 infection.