Long-term treatment with raloxifene results in decreased frequency and severity of collagen induced arthritis. Ovariectomized dilute brown agouti mice with collagen-induced arthritis were treated with raloxifene (60 μg/day; n = 11) (solid triangles) or vehicle control (Miglyol 812; n = 9) (solid squares). Treatment was administered 5 days per week from day 26 after immunization, when mice had developed arthritis, and until termination of the experiment on day 70 after immunization. Arthritis was considered present when signs of arthritis were identified in one joint for two consecutive assessments, or in >1 joint. Frequency (a) and severity (b) were evaluated every third day. Severity was graded 1–3 in each paw (maximum score of 12 per mouse), expressed as the mean ± standard deviation in each group. Raloxifene treatment decreased significantly both the frequency (P < 0·001) and the severity (P < 0·01 from day 47, and <0·001 from day 68) of the disease, compared with controls.