Résumé : Objective. To describe patterns of clinical and immunologic progression in children who are vertically infected with the human immunodeficiency virus. Methods. Children who were born to mothers who were infected with the human immunodeficiency virus in 11 European centers were enrolled at birth in a prospective study and followed according to a standard protocol. At each visit, a clinical and immunologic class was allocated according to guidelines of the Centers for Disease Control and Prevention (CDC). Progression to serious disease and death was assessed, allowing for available and actual antiretroviral therapy (ART). CDC class at each visit was assessed cross-sectionally. Results. More than 15% of infected children will have progressed to category C or death by age 1 year and nearly 50% by 10 years. Just under 20% of children will have evidence of severe immunodeficiency by age 1 and 75% by 10 years. In general, immune status poorly reflected clinical condition. Children who were born after 1994, when the recommendation of earlier initiation of more active therapy was introduced, were significantly less likely to progress than those who were born when treatment was not widely available or was largely confined to zidovudine monotherapy. Estimated progression to CDC class C or death initially was faster in untreated than in treated children, but by 10 years estimated cumulative progression was similar in both groups. Treatment started before class C disease was associated with significantly slower progression. Cross-sectional analysis showed that children largely are symptom-free throughout their lives. After 4 years of age, fewer than 25% of infected children had symptoms at any one time, irrespective of ART received. Conclusion. Vertically infected children are without serious symptoms or signs for most of the time. The prognosis has improved with more widespread availability and use of combination ART. These findings have implications for health, education, and other support-service provision.