Permanent atrial paralysis is a very rare entity characterized by absence of electrical and mechanical activity of the atria which persists for months or years. We present a patient with congestive cardiomyopathy and chronic atrial paralysis. The phonomechanocardiographic study confirmed the absence of mechanical contraction of the atrium and did not show atrial electrical activity in the superficial electrocardiogram nor in the intracavitary tracing. In the electrophysiological study of the biopsy of the atrial myocardium an unexcitable tissue was found with an important diastolic despolarization of 30 mv. The histologic and ultrastructural studies showed nonspecific changes, with the replacement of the myocardial cells by fibrous tissue.