Cardiac involvement in 32 acromegalics was related to endocrine parameters, clinical score and duration of the disease as well as compared to that of 50 controls free of cardiac disease. Stress ECG, 24h Holter monitoring and echocardiography revealed that supraventricular premature complexes did not occur more often in acromegalics than in controls, both prevalence and severity of ventricular arrhythmia, however, were higher in patients compared to controls: 15/32 (48%) acromegalics had complex ventricular arrhythmia as compared with 6/50 (12%) normal subjects (p less than 0.01). Repetitive ventricular arrhythmia was manifest in 10/32 (31%) patients but only in 4/50 (8%) controls (p less than 0.01). Furthermore, frequency of ventricular premature complexes increased with duration of acromegaly (p less than 0.01), the severity of the former being correlated with left ventricular mass and with clinical activity score (p less than 0.01). No correlation, however, was found between the degree of ventricular arrhythmia and hormone levels. Left ventricular muscle mass was increased (p less than 0.02) due to concentric hypertrophy. Thus, compared to controls, acromegalics show more frequent and complex ventricular arrhythmia and left ventricular hypertrophy. Duration of the disease rather than hormone levels seems to be relevant for these pathological changes.