Deletional α⁺-thalassemia (–α^3.7) was investigated in four groups of unrelated individuals from the Bantu population (newborns, normal adults, sickle cells trait carriers, sickle cell anemia patients) of Brazzaville, Congo. The frequency of the (–α^3.7) chromosome was similar between newborns (f = 0.40) and adult subjects (f = 0.36), and between sicklers and nonsickler subjects. The frequency of the (–α^3.7) chromosome in sickle cell anemia patients (SS patients) did not change when age was stratified. The hematological characteristics of SS patients with (–α/αα, –α/–α) and without (αα/αα) α⁺-thalassemia were similar to those reported in Jamaican and US sickle cell anemia patients. α⁺-Thalassemia had an effect on the percentage of hemoglobin S in sickle cell trait carriers. Thus, the high frequency of α⁺-thalassemia in the Congolese population presumably results from this disorder having a selective advantage favoring survival. However, the frequency of α⁺-thalassemia was not affected by age. Although in this selective tropical environment, α⁺-thalassemia as elsewhere markedly affects the hematological characteristics of sickle cell anemia patients, however our data provide no evidence that α⁺-thalassemia increases survival of SS patients.