Saguenay-Lac-St-Jean (SLSJ) is a rather geographically isolated region of Quebec which shows a high occurrence of hereditary disorders. It has been suggested that high inbreeding might explain this situation. We studied the inbreeding in the SLSJ region by 10-year periods from 1842 till 1971 using the Catholic Church dispensations. The values of the mean inbreeding coefficient were found to be low during the whole period, reaching a peak of 22.94 × 10–4 during the period 1902–1911. The values observed in the SLSJ were lower than those found in most regions of Quebec and similar to those reported in European populations.