To the Editor.— When the patient with coronary disease is "back on his feet" and regular daily exercise is considered essential to keeping him there, I prescribe indoor cycling, and the prescription is as specific as any written for his medication. There are many reasons for preferring indoor cycling to walking, swimming, jogging, and golf. It is less likely to result in accidents; it does not depend on the weather. A patient housebound by wintry blasts or spring rains can exercise regularly, unhampered by outdoor clothing. If tired, he need not look for a park bench or step to rest on. The exercise can be done at regular intervals throughout the day as prescribed. If the patient is a busy executive, he can install a cycle in his office as well as at home and take his exercise while on the job. Patients with back conditions may find some forms