A multicentre double-blind comparison of choline magnesium trisalicylate (CMT) and acetylsalicylic acid (ACSA) compared the two medications for seven weeks in rheumatoid arthritis patients. Investigators measured the number of painful and swollen joints and the duration of morning stiffness, and assessed the overall condition of each patient. Both medications were highly effective in significantly reducing the severity of symptoms flaring after interruption of prior therapy. CMT achieved a greater reduction in the number of swollen joints than did ACSA (P less than 0.05). The incidence of adverse side-effects per patient was significantly less with CMT (P less than 0.05) (ACSA 32.1%; CMT, 16.3%. A larger percentage of ACSA patients (50.8%) reported adverse side-effects than did CMT patients 28.4%) (P less than 0.02).