In Ontario, only about 10% of compensation patients with low back pain are disabled more than six weeks and hence tend to have chronic complaints. Six hundred and twenty-three such patients were studied to determine the distribution of diagnoses and to test the effectiveness of various programs of conservative therapy.Two hundred and thirteen patients were assigned in rotation to one of four treatments. The results were inconclusive. In 70% of these, the pain was due to intervertebral disc degeneration with added trauma.Two hundred and sixteen patients were assigned randomly to a treatment involving mild exercise, or one with vigorous exercise. Neither was found to be superior. In 76% of these, the pain was due to disc degeneration with added trauma.Using 194 patients, the results of treatment in the Compensation Board Rehabilitation Centre were compared with those obtained by treatment at home. Satisfactory improvement was achieved in 15 of 95 treated at home, and in 42 of 99 in the Centre. The failure of treatment in six of each 10 cases indicates that present-day methods of management of such patients are unsatisfactory.