Idiopathic haemochromatosis is an inborn error of metabolism as stated for the ht time by Sheldon (1935). The disease usually appears sporadically. However, after the initial case described by Frisch (1922), numerous reports of familial cases appeared in the literature (Boulin & Bamberger, 1953; Harvier, di Matteo & Deuil, 1947). Ita genetic nature has thus been suggested and several hypotheses have been put forward (Lawrence, 1935; Nee1 & Schull, 1954; Nussbaumer, Plattner & Rywlin, 1952; Pirart, 1954). However, no systematic investigation has been carried out from this point of view.

Progress in the study of iron metabolism provides a good opportunity for a new approach to the problem. In a previous study, some of us (Debrb, Schapira, Dreyfus & Schapira, 1952) pointed out that approximately 30 yo of the patients' relatives had a definite hypersideraemia, a finding which was later confirmed by Finch & Finch (1955). The present work is an attempt to draw some genetic conclusions from a broader biological investigation and from family studies. A preliminary communication of this work was given at the First International Congress of Human Genetics (Lamy, Schapira, Frhzal & Maroteaux,