Abstract The average inbreeding coefficients of the highly consanguineous Fur and Baggara tribes of Western Sudan were 0.04167 and 0.04450, respectively. Two hundred ninety‐eight subjects from the two tribes were tested for polymorphism of hemoglobins, seven red cell enzymes, and four serum proteins. The Baggara showed a higher gene frequency of Hb S and Tf D and lower gene frequency of Gd A and P C compared to the Fur. Both tribes showed a log gene frequency of PGM 1 and high frequency of G6PD deficiency when compared to other Sudanese tribes. In spite of the high degree of inbreeding, no significant deviation from the Hardy‐Weinburg equilibrium was observed in either tribe. The effects of inbreeding seem to be offset by mixing between the two tribes on Gabal Marra Plateau. The flow of the sickle gene from the Baggara into the Fur and other Sudanese tribes is discussed.