Twenty-five patients (14 males and 11 females aged 11 to 45 years) with rhythm disorders and valvular defects were operated on. Supraventricular paroxysmal tachycardia was the most common of rhythm disorders occurring in 15 cases, with Ebstein's anomaly in 11, mitral valve incompetence in 2, combined mitral defects in 1 and aortic stenosis in 1 of those. Atrial fibrillation was recorded in 7 patients, with Ebstein's anomaly in 2, mitral stenosis in 2, mitral incompetence in 2 and mitral prolapse in 1 of those. Nodal tachycardia was found in 1 patients with Ebstein's anomaly and in 1 patient with mitral valve incompetence. Left-ventricular tachycardia was diagnosed in a female patient with mitral prolapse. The operations were simultaneous and comprised two steps; they were performed under extracorporeal circulation and drug- and cold-induced cardioplegia, with the elimination (surgical interruption) of accessory conduction pathways or removal of arrhythmogenic areas as the first step, and reconstructive surgery on heart valves as the second step.