The correlation between several P wave measurements from the orthogonal electrocardiogram (SVEC III lead system) extracted by computer analysis and simple hemodynamic parameters related to ventricular dysfunction was studied in two groups of patients. Group I consisted of 32 patients with pulmonic valvular stenosis and intact interventricular septum. There was a significant correlation between electrocardiographic criteria of right atrial overload and the two hemodynamic parameters studied: peak pulmonic systolic pressure gradient and right ventricular end diastolic pressure (r=0.502, p<0.005 and r=0.661, p<0.001 respectively). Group II consisted of 49 patients with aortic valve disease. In this group, a significant correlation between the electrocardiographic parameters of left atrial overload and the left ventricular end diastolic pressure could be demonstrated only by a multivariate regression analysis (r=0.630, p<0.005). The P wave measurements that are well correlated with the ventricular end diastolic pressure can be considered as valuable criteria for atrial enlargement secondary to a decrease of ventricular compliance, such as seen in ventricular hypertrophy, failure or in ventricular constrictive or restrictive diseases. The pathophysiologic mechanisms of the influence of the ventricular overload (dysfunction) on the atrial function and the resulting P wave changes are discussed.