Document Type



A small riverine community, Portuchuelo (8o37’S, 63o49’W), and a rural county, Monte Negro (10o15′S, 63o18′W), both in the state of Rondônia, Brazil, were studied for the purposes of ascertaining health conditions and the causes of the variability of some infectious diseases. The sample included 181 inhabitants of Portuchuelo and 924 of Monte Negro. Data on 11 blood polymorphisms (ABO, Rh, MNSs, Kell, Fy, haptoglobin, hemoglobin, ACP1, PGM1, GLO1, and CA2) were used to determine the ethnic composition of the inhabitants of Portuchuelo and Monte Negro. The contributions of Africans, Amerindians, and Europeans to the ethnic composition of the studied populations were, respectively, 0.21 ± 0.046, 0.44 ± 0.064, and 0.35 ± 0.069 in Portuchuelo; and 0.25 ± 0.032, 0.12 ± 0.046, and 0.63 ± 0.054 in Monte Negro.