OBJECTIVES: To analyse mortality, loss to follow-up (LTFU) and retention on antiretroviral treatment (ART) in the first year of ART across all age groups in the Malawi national ART programme. DESIGN: Cohort study including all patients who started ART in Malawi's public sector clinics between 2004 and 2007. METHODS: ART registers were photographed, information entered into a database and merged with data from clinics with electronic records. Rates per 100 patient-years and cumulative incidence of retention were calculated. Subhazard ratios (sHRs) of outcomes adjusted for patient and clinic-level characteristics were calculated in multivariable analysis, applying competing risk models. RESULTS: A total of 117,945 patients contributed 85,246 person-years: 1.0% were infants below 2 years, 7.4% children 2-14, 7.5% young people 15-24, and 84.2% adults 25 years and above. Sixty percent of patients were female: women outnumbered men from age 14 to 35 years. Mortality and LTFU were higher in men from age 20 years. Infants and young people had the highest rates per 100 person-years for mortality (23.0 and 19.4) and LTFU (24.7 and 19.3), and the highest adjusted relative risks compared to age group 25-34 years: sHRs were 1.37 [95% confidence interval (CI) 1.17-1.60] and 1.17 (95% CI 1.10-1.25) for death and 1.37 (95% CI 1.18-1.59) and 1.27 (95% CI 1.19-1.35) for LTFU, respectively. CONCLUSION: In this country-wide study patients aged 0-1 and 15-24 years had the highest risk of death and LTFU, and from age 20 men were at higher risk than women. Interventions to improve outcomes in these patient groups are required.