Indirect systolic time intervals corrected for heart rate were measured at rest, during, and immediately after the isometric handgrip exercise in 70 patients with progressive muscular dystrophy, and these were compared with the values of normal subjects. Those with dystrophy included 47 patients with Duchenne type, 19 with limb girdle type and 4 with facioscapulohumeral type, and each type was subdivided into 2 groups by the severity of the skeletal muscle involvement: 1) mild group, included patients who were still able to walk, 2) severe group, included those who were restricted to wheel chair or confined to bed. Over a half of the patients of the severe Duchenne type group had a longer pre-ejection period (PEP), shorter left ventricular ejection time (LVET), and larger PEP/LVET ratio at rest than the normal group. Increased PEP/LVET ratio during and after isometric handgrip exercise was observed in the severe group of Duchenne type. The patients with limb girdle type, and facioscapulohumeral type showed no significant difference in values of the systolic time intervals at rest and during handgrip exercise compared with the normal subjects. The measurements of resting and exercise systolic time intervals may be useful for clinical recognition of latent left ventricular functional impairement in subjects with progressive muscular dystrophy.