The etiology of humeral epicondylitis and three different conservative methods of treatment were prospectively studied during two years in patients visiting a large occupational health center. Eighty-eight workers, 50 male and 38 female, out of 7600 suffered from humeral epicondylitis. The annual incidence was 59 per 10 000 workers. The mean age was 43 years. The main cause (61.4%) of tennis elbow was over-exertion of the finger and wrist extensors in trained workers. Forty-seven patients were treated with local corticosteroid and anesthetic injections (beta-methasone + lidocaine), 20 patients with methylprednisolone injections and 21 patients with wrist immobilization in combination with indomethacin. The result of therapy was excellent or good in 82% of the cases after six months and in 90% after one year. No significant differences (p greater than 0.1) in results were observed between patients treated with different therapies. Two patients (2.3%) were operated on after conservative treatment had failed.