Abstract Question What is the short-term risk of disease progression in children infected perinatally with HIV-1? Study design Meta-analysis. Main results Eight cohort studies and nine randomized controlled trials in 3941 children infected perinatally with HIV-1 were identified. The risk of AIDS or death increased across all age groups with decreasing CD4 T cell percentage (CD4%). Children aged ≤2 years had the most pronounced increase in risk within 12 months with decreasing CD4% compared with children aged 5 to 10 years (CD4% 1 1 Estimates are approximate as data were presented graphically. at which probability of death increases: 20% to 25% for children aged 6 months to 2 years vs. 10% to 15% for children aged 5 to 10 years; CD4% at which probability of AIDS increases: 25% to 30% for children aged 6 months to 2 years vs. 12% to 20% for children aged 5 to 10 years). Risk of disease progression increased with increasing viral load although the correlation was more gradual compared with CD4%. Authors’ conclusions Risk of disease progression in children infected with HIV-1 is strongly associated with low CD4%, particularly in children aged ≤2 years.