A multi-centre, double-blind, crossover study was carried out in 80 patients with rheumatoid arthritis to compare the efficacy and side-effect profiles of two formulations of indomethacin. Patients were allocated at random to receive 75 mg indomethacin per day either as 1 controlled-release tablet at night or as 1 immediate-release capsule given 3-times a day for a period of 4 weeks before being crossed over to receive the alternative treatment for a further 4 weeks. Pain scores, daily symptomatology and the requirement for escape analgesia recorded by both investigator and patient indicated that controlled-release indomethacin tablets, 75 mg given at night, was as efficacous as immediate-release indomethacin capsules given 3-times daily. However, the controlled-release formulation had a superior side-effect profile with a reduced incidence of abdominal/epigastric pain compared to the immediate-release preparation.