Thirty-six women aged 60, 70 or 80 years who had fractured one of their distal radii (Colles' fracture) 0 to 35 (median 10) years earlier were examined in this population-based study. Single photon measurements (SPA) were performed on both arms 1 cm and 6 cm proximal to the styloid process of the ulna. All women were questioned about earlier wrist fractures and which, if any, side had been affected. Information about the type and site of the fracture was also gathered from the hospital records. The bone mineral content (BMC) was found to be increased by almost 20% in the once-fractured radius at the distal measuring site (1 cm) when compared with the unaffected side. This difference did not seem to diminish with time. At the proximal measuring site there was no difference between the once-fractured and the non-fractured side. There was a progressive loss of bone mineral in the once-fractured arm during the first years after the fracture however. This appeared to be reversed after about 10 years to a relative gain, even though the correlation was weak. Six of the 36 women could not remember which side had been fractured and five could not remember having had such a fracture at all. Determination of osteoporosis by measuring forearm BMC with single photon densitometry is therefore of limited value in some women of the oldest age groups.