We performed a prospective, randomised trial on 106 patients to compare the effects of local corticosteroid injections with physiotherapy as advocated by Cyriax in the treatment of tennis elbow. The main outcome measures were the severity of pain, pain provoked by resisted dorsiflexion of the wrist, and patient satisfaction. At six weeks 22 of 53 patients in the injection group were free from pain compared with only three in the physiotherapy group. In the corticosteroid-treated group 26 patients had no pain on resisted dorsiflexion of the wrist compared with only three in the physiotherapy group. Thirty-five patients who had injections and 14 who had physiotherapy were satisfied with the outcome of treatment at six weeks. At the final assessment there were 18 excellent and 18 good results in the corticosteroid group and one excellent and 12 good results in the physiotherapy group. There was a significant increase in grip strength in both groups but those with injections had a significantly better result. After one year there were no significant differences between the two groups. Half of the patients, however, had received only the initial treatment, 20% had had combined therapy and 30% had had surgery. We conclude that at six weeks, treatment with corticosteroid injections was more effective than Cyriax physiotherapy and we recommend it because of its rapid action, reduction of pain and absence of side-effects.