Bone loss was evaluated in 118 patients with rheumatoid arthritis by measurement of the total width and marrow cavity of the second metacarpal bone. Both in men and women a significant increase in width of the medullary cavity could be demonstrated, probably due to bone loss at the endosteal surface. Although a certain increase in the total width of the second metacarpal bone took place in men but not in women, combined cortical thickness and metacarpal bone mass decreased significantly. There was no significant difference in the values in patients on gold treatment and in patients without systemic treatment, while patients treated with steroids demonstrated a significantly greater loss of endosteal bone compared to the other two groups. Some correlation was found between the severity of joint involvement and the measured loss of cortical bone. In summary, the study shows that bone loss takes place in patients with rheumatoid arthritis, being most pronounced in steroid-treated patients, in postmenopausal women, and in patients with more severe joint involvement.