BACKGROUND & AIMS: Hereditary hemochromatosis (HH) is an autosomal-recessive disorder characterized by iron overload. Relatives of HH patients were screened and those with HH-associated mutations and an increased iron load were identified. However, little is known about their mortality or strategies for their management. We assessed mortality among Swedish patients with HH and their first-degree relatives using health and census registers. METHODS: We performed a matched population-based cohort study of 3832 patients with HH and their 14,496 first-degree relatives using data collected from 1990 through 2007. Mortality data from these groups were compared with that of 38,969 population controls and their 143,349 first-degree relatives using Cox regression analyses. RESULTS: Patients identified on the basis of hospitalization with HH had an increased risk (relative risk [RR]) for death (RR, 2.45; 95% confidence interval [CI], 2.27-2.64; 857 deaths). Patients identified through other means had a mortality risk that was lower than those identified in the hospital but higher than controls (RR, 1.15; 95% CI, 1.00-1.33; 216 deaths). Their first-degree relatives had only a marginally increased mortality risk (RR, 1.05; 95% CI, 1.01-1.10); this RR was similar to that of patients' spouses (RR, 1.09; 95% CI, 0.86-1.38; 82 deaths). Patients with HH who also had a family history of HH did not have an increased mortality risk compared with other groups (RR, 1.05; 95% CI, 0.67-1.62; 21 deaths). CONCLUSIONS: Patients with HH have a modestly increased mortality risk compared with controls. The mortality of relatives is increased marginally compared with controls, and is similar among biological and nonbiological relatives.