The total inbreeding coefficient of a group of 574 individuals with autosomal recessive disorders (ARD) from Saguenay-Lac-Saint-Jean, a geographically isolated region of northeastern Quebec, was estimated from isonymy and compared to the mean inbreeding coefficient calculated from the genealogies. Its value was compared to that of 1722 matched controls. The total inbreeding coefficient was similar in both ARD and control groups, but higher than the values calculated from the genealogies. Most of the increase was due to the random component of inbreeding. This isonymy study confirmed that the high frequency of ARD in Saguenay-Lac-Saint-Jean is mainly the result of founder effect and genetic drift.