We quantified HFE genotype frequencies in specimens submitted by physicians grouped by specialty and determined associations of genotypes with initial diagnosis based on phenotyping in patients evaluated at an iron disorders center. Of 526 specimens (519 from Alabama), these "typical" hemochromatosis-associated genotypes were detected: 85 C282Y/C282Y, 50 C282Y/H63D, and 27 H63D/H63D. Respective frequencies of C282Y/C282Y in specimens from an iron disorders center (n = 156), gastroenterologists (n = 147), hematologists/medical oncologists (n = 85), liver transplant surgeons (n = 11), endocrinologists and rheumatologists (n = 9), and "other sources" (n = 7) were greater (p < 0.05) than in population controls. In 44 patients from an iron disorders center initially diagnosed as "presumed hemochromatosis," 27 (61.4%) had C282Y/C282Y, 10 (22.7%) had C282Y/H63D, and 3 (6.8%) had H63D/H63D. C282Y/C282Y was not detected in 48 patients with "abnormality probably not an iron overload disorder." A total of 20.5% of 44 family members of patients had "typical" hemochromatosis-associated HFE genotypes (7.0% controls; p = 0.02). We conclude that most physicians who submitted specimens identify patients by phenotyping who have greater frequencies of "typical" hemochromatosis-associated HFE genotypes than controls, and that HFE mutation testing is useful in detecting hemochromatosis in family members of persons with hemochromatosis or iron overload.