From 1976 to 1984, 31 patients underwent enlargement of very small aortic roots using autologous pericardial strips the subannular part of which extended into the incised anterior mitral valve leaflet. The majority of these interventions (n = 24) were carried out before the end of 1980. Over an average follow-up period of 52.5 months, only one of the surviving patients had a complication traceable to the pericardial implantation (aneurysmatic patch dilatation), and 2 late deaths were also not directly connected with the type of surgical procedure. Objective findings for evaluating the hemodynamic status and behavior of the patch material were attained in a total of 14 patients by heart catheterization and angiography. Eleven patients were examined twice at an average of 2.5 months, and 11 at an average of 52.5 months. Eight of latter patients had undergone an early postoperative investigation. The hemodynamic results after prosthetic valve replacement and aortic annulus enlargement was satisfactory in those examined. No evidence could be found in any patient of disturbance of the mitral valve's function, paravalvular leakage at the aortic prosthesis, or obstruction of the left ventricular outflow tract caused by this operative technique. Progressive patch dilatation which had already been proved at the first examination was observed in one case. These results verify not only the efficiency of this technique for the enlargement of a small aortic root in the frame of prosthetic valve replacement, but especially the suitability of autologous pericardium as patch material for this purpose.