Objectives. To assess paediatric antiretroviral treatment (ART)outcomes and their associations from a collaborative cohortrepresenting 20% of the South African national treatment programme.Design and setting. Multi-cohort study of 7 public sectorpaediatric ART programmes in Gauteng, Western Cape andKwaZulu-Natal provinces. Subjects. ART-naive children (.16 years) who commenced treatment with .3 antiretroviral drugs before March 2008.Outcome measures. Time to death or loss to follow-up were assessed using the Kaplan-Meier method. Associations between baseline characteristics and mortality were assessed with Cox proportional hazards models stratified by site. Immune status, virological suppression and growth were described in relation to duration of ART.Results. The median (interquartile range) age of 6 078 childrenwith 9 368 child-years of follow-up was 43 (15 - 83) months, with 29% bein