A genetic analysis of the segregation of hereditary hemochromatosis, indexed by the measurement of latent capacity of transferrin (LCAP), was undertaken in an ascertained sample of 147 pedigrees from Brittany, France. There were no mean differences by sex in the distribution of LCAP in the control sample, although in the family data there was a higher representation of males with low values than of females with low values, consistent with the higher proportion of affected males. The results of bivariate segregation analysis revealed no systematic evidence for heterozygous expression either in the biochemical domain of LCAP abnormalities or in increased liability to overt symptomatic disease. Joint consideration of the quantitative variable with hemochromatosis affection status allowed clear resolution of a recessive single-gene inheritance pattern in these families.