Seventy patients with primary fibrositis satisfying Smythe's criteria were studied in a 9-week double-blind trial comparing 50 mg amitriptyline with placebo. Fifty-nine patients completed the trial: 27 were treated with amitriptyline, and 32 took a placebo. The patients who received amitriptyline improved significantly in their morning stiffness and pain analog scores at 5 and 9 weeks, compared with baseline scores, whereas no changes were noted in these parameters in the placebo group. Fibrocytic point tenderness did not improve significantly in either of the treatment groups. When compared with the placebo group, the amitriptyline group improved significantly with respect to sleep pattern and patient and physician global assessments. Our data indicate that amitriptyline has some therapeutic benefit in patients with primary fibrositis.