Homozygosity for a 32-bp deletion in the CCR5 gene (CCR5delta32) has been shown to confer resistance to infection with the macrophage-tropic strain of human immunodeficiency virus (HIV) type 1. We examined the distribution of CCR5delta32 in 47 children (age range, 1.5 to 19 years), of whom 43 were infected with HIV, by the perinatal route (n = 41) or by the intravenous route (n = 2). The infected patients were classified as rapid progressors (RP) (n = 7) (CDC category C3 or death by 2 years of age), non-rapid progressors (NRP) (n = 17) (survival for > or =8 years after infection), or intermediate (n = 19). CCR5delta32 heterozygosity was found in two HIV-infected children, both NRP. None of the subjects were homozygous for CCR5delta32, and the remaining children had no evidence of CCR5delta32. The presence of CCR5delta32 heterozygosity in 4.8% of this, predominantly non-Caucasian population is consistent with the published distribution of the mutation. The finding that CCR5delta32 was present only in NRP and not in any RP is in agreement with previous reports suggesting that heterozygosity for CCR5delta32 may confer limited protection from disease progression.