Distribution of the HbS and HbC in the Guinean Republic was determined by the analysis of the excerption of 2213 inhabitants representing different ethnic groups of the country. It was found that the mean frequency of the HbS heterozygotes is 21.2 +/- 0.9% and of the HbC heterozygotes is 2.6 +/- 0.3%. Among major nationalities of the country the frequencies of the HbS heterozygotes make up 21.0 +/- 1.9% for the Fulbe, 22.2 +/- 1.6% for the Malinke and 26.5 +/- 1.6% for the Susu and frequencies of the HbC heterozygotes make up 3.0 +/- 0.8% for the Fulbe, 2.5 +/- 0.6% for the Malinke and 1.6 +/- 0.4% for the Susu. Relative viability of the HbS and HbC carriers for major Guinean nationalities is estimated. The relative fitnesses account is 1.05-1.13 for HbC heterozygotes and 1.07-1.16 for HbC heterozygotes.