Low bone mass is a frequent abnormality in patients with rheumatoid arthritis (RA) and may relate to the disease in different ways. Firstly, localised, juxta-articular bone loss is a common phenomenon and may be directly related to joint inflammation. Secondly, generalised bone loss has been suggested as an extra-articular manifestation of RA, and several factors, including disease activity and reduced mobility, have been implicated in its pathogenesis. Finally, patients with RA are treated with a variety of agents that may affect bone mass, including glucocorticoids. However, whether low dose glucocorticoid treatment contributes to generalised osteoporosis in patients with RA is a matter of debate. Some have suggested that positive influences on disease activity and mobility may outweigh their deleterious effects on bone. In this review we will focus on the association between generalised osteoporosis and RA, and on the effects of low dose glucocorticoid treatment on bone mass in these patients, including data that have been presented at recent scientific meetings. Abnormalities in bone metabolism and calcium regulating hormones, or strategies for the management of osteoporosis in patients with RA, are not included. These topics have been reviewed recently elsewhere. Before discussing currently available data we would like to mention some special problems related to bone mass measurements and to the design of studies dealing with bone mass in patients with RA.