We present the raw data from a study done on the incidence of osteoporotic hip fractures on Ischia, an island facing the Bay of Naples. Its 43,975 inhabitants form a well-defined, stable and homogeneous population. Since no air transportation to the mainland is available for residents, acute health care is provided by the sole local hospital. We carried out a discharge data survey by reviewing the hospital medical records from 1980-1989. During that decade, 148 residents (111 women, 37 men) had new hip fractures. The age-sex adjusted incidence for the population aged 50 years or more was 170.3 cases/100,000/year [95% confidence interval (CI) = 144.8-195.9] (women = 241.4 with 95% CI = 211.0-271.9; men = 79.4 with 95% CI = 62.0-96.9). Age-specific rates increased with age and were higher among women only over 60 years old. On the basis of the 1981 census and comparison of age-adjusted rates, we determined that incidence rates of these fractures for men and women on Ischia are among the lowest in the world: Ischian men have a hip fracture incidence second only to that of South African Bantu males. The female/male ratio on the island, one of the highest reported, is 3.05:1. Our data suggest that further studies on Ischia may provide important clues regarding risk and/or protective factors for hip fracture.