populations Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil

A sample of 103 randomly chosen healthy individuals from Alegrete, RS, Brazil, was tested for the CCR5∆32 allele, which is known to influence susceptibility to HIV-1 infection. The CCR5∆32 allele was identified by PCR amplification using specific primers flanking the region of deletion, followed by electrophoresis on a 3 % agarose gel. The data obtained were compared to those reported for other popula-tions and interpreted in terms of Brazilian history. The individuals studied came from a highly admixed population. Most of them were identified as white (N = 59), while blacks and browns (mulattoes) were N = 13 and N = 31, respectively. The observed frequencies, considering the white, black and brown samples (6.8, 3.8, and 6.4%, respectively), suggest an important European parental contribution, even in populations identified as black and brown. However, in Brazil as a whole, this allele shows gradients indicating a relatively good correlation with the classification based on skin color and other physical traits, used here to define major Brazilian population groups