[Infant mortality: heredity and environment]

An analysis of familial liability to infant mortality is presented. Heritability estimates for three periods of the demographic evolution of an isolated population (Isle-aux-Coudres, Quebec) are provided. Average heritability is on the order of 27%. This is interpreted as being partly due to sibs common environment and partly to dominance variance effects of genes. The real additive variance of the familial liability might well be nil.