The results of prospective noninvasive cardiologic investigations, including echocardiography and Holter monitoring are described in 2 siblings with juvenile ceroid lipofuscinosis of the Spielmeyer-Vogt-Sjogren type. In the elder patient, echocardiography revealed ventricular hypertrophy with slowed ventricular relaxation. Holter monitoring showed not only bradycardia but also slow and fast ectopic atrial rhythms, sinus arrests and complex ventricular ectopic activity including ventricular tachycardia. In the younger patient the findings were less severe. These functional disturbances due to cardiac involvement, never reported before in this disease, are discussed.