The genetic structure of Rondônia State is very heterogeneous due to the high migration indexes observed mainly from the second half of the Twentieth Century on. Since it is an endemic region for Malaria, we were able to observe an artificial selection in the fixation of some genes, from among the S an C hemoglobin?s variants. However, despite having a significant in the fixation of the black ethnic group (?24 = 12,04, p = 0,014), there was not a significant association of genes that are considered ethnical markers, like the HbS, when the Hemoglobin and the Ethnic Group?s phenotypes were analyzed together (?23 = 6,40, p = 0,94, for Blacks; ?23 = 3,76, p = 0,28 for Whites and ?23 = 3,53, p = 0,37 for Mulattos). With the use of these phenotypes in the P1 and F1 generations from Candelaria was significant ant 0,05 (?22 = 6,95, p = 0,031), fact that was not repeated when the distribution was done by age (?24 = 7,88, p = 0,09). Nevertheless, we stress that there was no symptomatic phenotype in the individuals age between 0-23 years. We observed a frequency of 0,03 and 0,05 for HbF, in the P1 and F1 generation from Candelaria, respectively. For these very generations, we observed 0,03 and 0,02 frequency distribution for the HbS and 0,006 and 0,02 for the HbC. In the conjoint analysis of Malaria and Hb phenotypes, we found a significant deviation for the normal Hb and Malaria (?22 = 23,64 , p = 0,00) and absence of Malaria and variant Hb phenotypes (? 22 = 10,45, p = 0,005).