The purpose of the present study was to determine the predictive ability of a single bone mineral density (BMD) measurement on a 25-year perspective. A group of 1076 women (age 20-78 years) had had their forearm BMD measured from 1970 to 1975. In those women that were still alive at the end of 1994 (n = 410), all fragility fractures (distal end of the radius, proximal end of the humerus, hip, and vertebra) that had occurred after the BMD measurement and that were roentgen verified were recorded, after a follow-up time of 20-25 years. Altogether, 213 fractures occurred in the cohort. In the age group > or = 40-70 (at time of BMD measurement) the relative risk (RR) associated with a 1 SD decrease of forearm BMD was 1.66 (CI 1.13-2.46) for a hip fracture (n = 43), 1.79 (CI 1.22-2.62) for a vertebral fracture (n = 63), and 1.33 (CI 1.20-1.73) for all fractures. In the age group 30-50, a fracture of the distal end of the radius after 20 years could be predicted; RR 1.90 (CI 1.02-3.55). These are slightly lower predictive values compared with previous studies of the same population with follow-up times of 11 and 13 years, especially with regard to hip fractures. However, the present study demonstrates that a single BMD measurement at the forearm has a predictive ability for fragility fractures--including hip fractures--on a 25-year perspective.