SummaryHeterozygous 4.1 hereditary elliptocytosis results from the absence of one haploid set of protein 4.1, a major component of the red cell skeleton. Two successive epidemiological investigations revealed fifteen probands in the French Northern Alps. The frequency of this disease seems to be very high in four small villages isolated in the Aravis mountains. The genealogical study shows that eleven probands share common ancestors who lived eight or ten generations ago in these villages. Thus there was probably a founder effect (...) from one pair of ancestors, strengthened by endogamy. In contrast, four probands originate from another area and are not genealogically related. Recent results in molecular genetics support the present data. (shrink)