In view of the reports of Globus1and others on the presence of definite myocardial lesions in patients with progressive muscular dystrophy, it seemed of interest to study some phases of the functional integrity of the circulation in a group of such patients. Accordingly, we studied the heart rate of seven patients with progressive muscular dystrophy. Dr. S. P. Goodhart placed the clinical material at our disposal. METHOD The studies were carried out with the aid of the cardiotachometer,2an instrument devised by one of us, which automatically records the heart rate of subjects for indefinite periods of time under all degrees of physical activity and rest. The action current of the heart is led from the chest by two electrodes, through 100 feet of light wire to a radio amplifier, which amplifies it about 6,000 times. The amplified current actuates a relay system, which in turn operates an electro-magnetic