The aim of this epidemiologic population survey was to assess the penetrance of the most frequent hemochromatosis (HFE) gene variants in ethnic Danish men. A cohort of 6,020 men aged 30-53 years was screened for HFE C282Y, H63D, and S65C variants by restriction fragment length polymorphism analysis. Subsequently, iron status markers (serum transferrin saturation, serum ferritin) were analyzed in 1,452 men. The C282Y allele was present in 5.6%, H63D in 12.8%, and S65C in 1.8% of the men. We found 23 out of 6,020 (0.38%) C282Y homozygotes, of whom two had been treated with phlebotomy. Among untreated C282Y homozygotes (n = 21) with available iron status markers (transferrin saturation n = 18, ferritin n = 16), 89% had elevated transferrin saturation >or=50%, 94% had elevated ferritin >or=300 microg/L, and 88% had elevation of both iron status markers; seven out of 16 (44%) had ferritin values >800 microg/L. One C282Y homozygote had normal iron status markers possibly due to nonexpressivity. Among C282Y/H63D compound heterozygotes (n = 66), 23% had elevated transferrin saturation, 27% elevated ferritin, and 9% elevation of both iron status markers. Among H63D/H63D homozygotes (n = 74), 15% had elevated transferrin saturation, 19% elevated ferritin, and 5.4% elevation of both iron status markers. Among C282Y/wild type (wt) heterozygotes (n = 255), 9% had elevated transferrin saturation, 9% elevated ferritin, and 1.2% elevation of both iron status markers. Among H63D/wt heterozygotes (n = 600), 8% had elevated transferrin saturation, 12% elevated ferritin, and 2% elevation of both iron status markers. None of the men with the S65C variant displayed elevation of both iron status markers. In conclusion, this study demonstrates a high penetrance of the C282Y variant in Danish men followed by the H63D variant while the S65D variant had no significant impact on iron status markers.