Current surgical practice regarding valve replacement has as its primary concern the appropriateness of tissue versus mechanical prostheses and perhaps lesser emphasis has been placed on the size of the device. Despite technical advances, which provide maximal valve orifice area in valve substitutes, small device implantation may be accomplished in the aortic root but not effectively relieve the obstructive nature of the original disease. We reviewed 39 patients who had undergone aortic valve replacement (AVR) for aortic stenosis (AS) and had preoperative and postoperative (6 months-3 years) echo measurements which permitted calculation of the left ventricular mass (LVM) and mass index (LVMI). The mean age for the 32 women and 7 men was 67.4 years (22-83). There were four groups as determined by prosthetic size and aortic root enlargement (ARE) or not. The majority of the prostheses were heterografts (26), and the others were tilting discs or bileaflet. There was no difference (P = ns) in preoperative NYHA class, cardiopulmonary bypass (CPB) time, cross-clamp time, associated procedures or complications among the four groups. Although all groups demonstrated a reduction in LVM and LVMI, there was a greater and equal mass and mass index reduction in patients receiving a 21 mm prosthesis or larger. Despite the refinements in artificial valve designs, the 19 mm size valves may not provide comparable reduction in LVM and LVMI following AVR for AS, and the aortic root enlargement permits a larger prosthetic implantation and greater potential for reduction in LVM and LVMI without an increase in the operative time or postoperative complications.