PURPOSE: To study the clinical outcomes of subjects who are homozygous for the C282Y mutation of the hemochromatosis gene.SUBJECTS AND METHODS: All patients referred to a tertiary referral centre for hemochromatosis were included. The study also included 16 C282Y homozygotes detected in a population screening study.RESULTS: The study comprised 277 C282Y homozygotes, including 16 nonexpressing C282Y homozygotes. The mean follow-up period was 7.3 years (range zero to 44 years). The actuarial survival rates of C282Y homozygotes at five, 10 and 20 years were 95%, 93% and 66%, respectively. Life-threatening diseases (cirrhosis, hepatocellular carcinoma, diabetes, heart disease) were present in 36% of male C282Y homozygotes and 19% of female C282Y homozygotes. Cirrhosis of the liver and diabetes were the major clinical symptoms affecting long term survival. Only one nonexpressing homozygote required venesection therapy during the follow-up period.CONCLUSIONS: Long term survival is excellent in C282Y homozygotes diagnosed and treated before the development of cirrhosis and diabetes.