Objectives. To introduce the combined South African cohortsof the International epidemiologic Databases to EvaluateAIDS Southern Africa (IeDEA-SA) collaboration as reflectingthe South African national antiretroviral treatment (ART)programme; to characterise patients accessing these services;and to describe changes in services and patients from 2003 to2007.Design and setting. Multi-cohort study of 11 ART programmesin Gauteng, Western Cape, Free State and KwaZulu-Natal.Subjects. Adults and children