The impact of primary hyperparathyroidism (HPT) on the population has not been well documented, and even less information is available for asymptomatic HPT. Only 57 deaths were attributed to the condition in the United States in 1986, for a reported HPT death rate of 0.24 per million per year. Many more patients were affected, however, and the incidence of hospitalization for HPT was 6.6 per 100,000 in 1986, counting all listed diagnoses, and 2.9 per 100,000 counting only first-listed diagnoses. Surgery was performed on approximately 10,000 hospitalized patients in the United States in 1986, for a parathyroidectomy rate of about 4.2 per 100,000 per year. When nonhospitalized cases are included, the rates are even higher. The estimated annual incidence of HPT was 42.1 per 100,000 in Rochester, Minnesota in 1974-1976; the prevalence of HPT was 4.3 per 1000 in a population survey in Sweden. By any of these measures, HPT is more common in women than men and increases with aging in both sexes. The potential cost of HPT could be as high as $420 million/year in the United States, but no formal estimates have been made. Disability related to HPT or its treatment has not been quantified; randomized clinical trials to determine the utility of parathyroidectomy have not been performed; and no assessment of cost benefit or cost effectiveness of any therapeutic modality has been carried out. Until patient management and cost issues are resolved, it is premature to consider an aggressive program to screen the general population for HPT.