ABSTRACT: BACKGROUND:Urgent antiretroviral therapy (ART) among hospitalised HIV-infected children might accelerate recovery or worsen outcomes associated with immune reconstitution. We aimed to compare urgent versus post-stabilisation ART among hospitalised HIV-infected children in Kenya. METHODS:In this unmasked randomised controlled trial, we randomly assigned (1:1) HIV-infected, ART-naive children aged 0-12 years who were eligible for treatment to receive ART within 48 h (urgent group) or in 7-14 days (post-stabilisation group) at four hospitals in Kenya (two in Nairobi and two in western Kenya). We excluded children with suspected or confirmed CNS infection. A statistician not involved in study procedures did block randomisation with variable block sizes generated using STATA version 12. We followed children for 6 months for primary outcomes: mortality, drug toxicity, and immune reconstitution inflammatory syndrome (IRIS). We did all analyses in a modified intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT02063880. FINDINGS:We began enrolment on April 24, 2013, and completed follow-up on Nov 17, 2015. We enrolled 191 (76%) of 250 hospitalised HIV-infected children. Of these, 183 children were randomly assigned: 90 to urgent ART and 93 to post-stabilisation ART. 181 (99%) of 183 children were included in the modified intention-to-treat analysis. Median age was 1·9 years (IQR 0·8-4·8). Baseline sociodemographic, clinical, and virological characteristics did not differ between groups except median CD4 cell percentage, which was lower in the urgent group (13% [IQR 9-18] vs 17% [IQR 9-24]; p=0·052). Of 181 admission diagnoses, 118 (65%) were pneumonia, 58 (32%) malnutrition, and 27 (15%) suspected tuberculosis. Median time to ART was 1 day (IQR 1-1) in the urgent group and 8 days (IQR 7-11) in the post-stabilisation group. Overall, mortality risk at 6 months was 61 per 100 person-years. Mortality risk did not differ by group (70 per 100 person-years in the urgent group vs 54 per 100 person-years in the post-stabilisation group; hazard ratio [HR] 1·26, 95% CI 0·67-2·37) p=0.47, even after adjusting for baseline CD4 cell percentage (adjusted HR 1·30, 95% CI 0·69-2·45; p=0·41). The incidence of IRIS, and drug toxicity was not significantly different between trial arms. There were no differences between treatment groups in the proportion of grade 3 or 4 adverse events (34 [38%] of 90 children in the urgent group vs 40 [44%] of 91 children in the post-stabilisation group; p=0·40) or the proportion of any change in ART regimen (five [7%] vs six [8%]; p=0·79). We discontinued randomisation at interim review when the futility boundary was crossed. INTERPRETATION:Early mortality risk was extremely high among hospitalised HIV-infected children. Urgent ART did not improve survival. FUNDING:National Institute of Child Health and Human Development, National Institutes of Health, USA.