Bone samples from the rim of the iliac crest were obtained at autopsy from 59 patients aged 23 to 75 years, of whom 10 men and 10 women aged 50-75 years had osteoarthritis diagnosed by hand X-rays. An equal number in the same age group and 10 men and 9 women aged less than 50 years were without osteoarthritis. After embedding the bone in PMMA, the blocks were cut, polished, and coated with carbon. The fractions of bone falling within four consecutive bands of signal level were derived from digital backscattered electron imaging. Normal males had more low and medium density bone and normal females more very high density phase tissue proportionately. In both male and female osteoarthritis cases, low and medium fractions were low. The very high density fraction was mainly calcified fibrocartilage; when it was excluded from the calculations, the low, medium, and high phases occurred equally in normal males but increased stepwise in normal females and in osteoarthritis cases of both sexes. The results suggest a lower rate of bone renewal in females than males, and in male osteoarthritis subjects than normal males. An increased proportion of bone of high density would reduce the quality of the bone by increasing its stiffness.