To evaluate the occurrence of infections in asymptomatic and symptomatic human immunodeficiency virus (HIV)-infected children we performed a prospective comparative cohort study. Twenty-seven HIV-infected children were individually matched with paired immunocompetent controls and followed up for a total of 543 months (mean per child, 19.4 +/- 11 months). Collected data were evaluated considering HIV-infected children both as a whole and as P1 and P2 patients according to the Centers for Disease Control classification. Twenty-seven HIV-infected children had 185 infectious episodes vs. 27 matched controls who experienced 118 infections. P1 children had a number of infections similar to those of normal controls (99 vs. 86) whereas P2 children had a significantly higher number of infections than did controls (86 vs. 32). Pneumonia and oral candidiasis occurred significantly more frequently in symptomatic HIV-infected children than in normal controls. Severe infections occurred almost exclusively in HIV-infected symptomatic children.