Hereditary haemochromatosis is one of the most common genetic disorders affecting populations of European ancestry. Isolation of a strong candidate gene, the HFE gene, allows genetic diagnosis in a large number of cases. However, different mutation frequencies have been reported in hereditary haemochromatosis patient populations from various geographic regions. Such data and phenotype-genotype correlations from Swiss patients with hereditary haemochromatosis are lacking. The objective of our study was to determine the frequency of HFE gene mutations in Swiss patients with hereditary haemochromatosis and to describe the clinical phenotype of patients with either a homozygous C282Y mutation or compound heterozygotes. 71 patients with a clinical diagnosis of hereditary haemochromatosis were identified through a questionnaire sent to physicians caring for hereditary haemochromatosis patients. Pertinent clinical data, in particular those reflecting iron body stores, were collected. Genotyping for the C282Y and H63D mutation of the HFE gene was performed. In 90% of the cases a mutation of the HFE gene was found. 86% of the patients were homozygous for the C282Y mutation, 4% were compound heterozygotes for the C282Y and the H63D mutation. Patients with the homozygous C282Y mutation showed a broad phenotypic spectrum that could not be accounted for by age or sex differences only. Our results demonstrate that within the Swiss population genetic testing can also identify the vast majority of patients with hereditary haemochromatosis. However, the diagnosis is not ruled out by a negative genetic test. Furthermore, a broad phenotypic spectrum is associated with the homozygous C282Y mutation in Swiss hereditary haemochromatosis patients. The implications of these findings for planning of widespread genetic screening for hereditary haemochromatosis in the general population are discussed.