Background/Aim. Aortic valve disease - stenosis and regurgitation are the cause of increased homodynamic stress of the left ventricle (LV) which then develops an adaptive mechanism of cardiac muscle hypertrophy. The aim of this study was to establish if aortic valve replacement procedure (AVR) reduces myocardial hypertrophy and if it does in what period of time. Methods. Eighty-six patients who had been operated for AVR in the Clinical Center of Serbia were included in this investigation. In the every patient the aortic valve had been replaced with a mechanical valve prosthesis. Transthoracic echocardiography examination (TTE) was performed in all of the patients before, and one week after the operation, while 22 patients were followed-up on a long term basis. The LV mass was determined with the formula according to the Pen convention. Results. In the tested group there was significantly more male than female individuals (n = 57-66.3%, 29-337%). Twelve patients (14%) were operated for isolated aortic stenosis, 22 patients (25.6%) for aortic regurgitation, 48 patients (55.8%) for combined aortic valve disease, while 4 patients (4.7%) for endocarditis. Student t test did not show any significant difference in diastolic septal thickness before and after the operation (p = 0.88), while it did show that the difference in the LV mass before and after the operation was highly significant (p = 0.000). This test also showed that, taking the mass of 240 g as the border value for hypertrophy of LV, the reduction of LV mass between preoperative and early postoperative finding was not significant (p = 0.5), while the reduction in LV mass between late and early postoperative examination was statistically significant (p = 0.000). In 19 of 22 patients who were followed-up postoperatively over a long period (84 months after the operation) significant reduction of LV mass was registered. The mean time of the reduction was 27.5 months. Conclusion. This study showed the presence of a significant reduction in the LV mass after AVR, and that the mean time required for this process was more than two years.