We analyzed the hemoglobin patterns of all the adult patients whose hemograms, performed in the hematology laboratory of our hospital, indicated microcytosis (MCV < 82 fl). During a 6 weeks period, 43 cases of microcytosis were identified out of 1827 hemograms and, among them, 16 cases of beta-thalassemia trait were diagnosed, i.e., 0.88%. This rate can probably be extrapolated to the general population of this region. It is in agreement with results obtained by other authors from southeastern France. This frequency of heterozygous beta-thalassemia is non-negligible and strongly suggests that screening for the beta-thalassemia trait in the at risk populations should be undertaken to prevent homozygous forms.