Summary:The effects of chemokine and chemokine receptor genetic polymorphisms such as stromal derived factor 1 (SDF1-3´A), CCR2-64I, and CCR5-&Dgr;32 associated with HIV-1 transmission and/or rate of disease progression in infected study subjects remain highly controversial and have been analyzed primarily only in adults. We have investigated whether these polymorphisms may provide similar beneficial effects in children exposed to HIV-1 perinatally. The prevalence of CCR2-64I allele was significantly increased (p= .03) and the CCR2-64I genotype distribution was not in Hardy-Weinberg equilibrium, among HIV-1–exposed uninfected infants. Moreover, in the HIV-1–infected group, a delay to AIDS progression was observed among carriers of CCR2-64I allele. This is the first report that suggests a protective role of CCR2-64I allele in mother-to-infant HIV-1 transmission and documents a delay in disease progression, after the child has been infected with HIV-1. However, SDF1-3´A and CCR5-&Dgr;32 alleles did not modify the rate of HIV-1 transmission or disease progression in HIV-1–infected children.