We reviewed the records of 37 patients with myasthenia gravis treated with azathioprine (n = 10) or cyclophosphamide (n = 27). All patients had received prednisone and anticholinesterase therapy, and most had undergone thymectomy prior to immunosuppressive therapy. Thirty patients (81%) responded to treatment. Both azathioprine and cyclophosphamide were found to be effective in the treatment of myasthenia gravis. The degree of improvement was more pronounced in patients with thymoma.