Abstract The main coreceptor gene involved in HIV-1 infection is CCR5 β chemokine receptor gene for which several mutations have been described, some of which have correlated with HIV-1 infection, acquired immune deficiency syndrome (AIDS), or both. Deletion of 32bp in the CCR5 gene (Δ32) has been shown to confer resistance to infection by HIV-1 R5 strains. Another mutation, characterized by a thymine to adenine (T to A) nucleotide substitution at position 303 (m303), has shown the same effects as the Δ32 mutation, with previous studies having shown that the allele frequency of the CCR5-m303 mutation is 0.014 in African-American and 0.007 in French populations. The Brazilian population is known to be genetically diverse, because of which we investigated the allele frequency of the CCR5-m303 mutation in three different Brazilian ethnic groups containing individuals who were not infected with HIV-1 and also in a cohort of HIV-1 long-term non-progressors. We used the polymerase chain reaction (PCR) and HincII restriction fragment length polymorphisms (RFLP) to investigate these populations and found that none of the 566 individuals examined the mutant CCR5-m303 allele. These results are in accordance with the previously reported allelic frequencies for African-American and Caucasian populations and may reflect the real prevalence of the m303 mutation in Brazil.