Pericardial heart valve bioprostheses have been utilized for 20 years. In spite of encouraging initial results, long-term follow-up showed a higher incidence of structural failures and primary tissue failures than porcine bioprostheses. Pericarbon represents the newest generation of bovine pericardial bioprostheses. Aim of this study is the long-term evaluation with echocardiographic and color Doppler technique of an innovative bioprostheses, in particular, its morfological and functional characteristics. From 1985 to 1989, 78 consecutive patients (21 males, 57 females, mean age 56.5 +/- 8.16 years) underwent mitral valve replacement with Pericarbon 29, by the same operator, who preserved the mitral posterior leaflet. One month after operation, 21 of these patients underwent echo-color Doppler evaluation, in normalized hemodynamic conditions (normality ranges). In 1995, at the end of the followup, 30 of the remaining 54 patients underwent new echo-color Doppler evaluation and these data were compared with normality ranges values. Leaflets' thickness increased from 0.98 +/- 0.09 to 2.87 +/- 0.73 mm (anterior leaflet; p < 0.0001) and from 1.02 +/- 0.08 to 2.71 +/- 0.45 mm (posterior leaflet; p < 0.0001) 43.3% of anterior leaflet and 53.3% of posterior leaflet showed fibrocalcic lesions. Mean transvalvular gradient increased from 3.4 +/- 0.2 to 6.6 +/- 3.4 mmHg (p < 0.0001); also functional area decreased (p < 0.0001). We have found no paraprosthetic regurgitation and a very low number of central prosthetic regurgitation. Left ventricular function, evaluated by ejection fraction and regional kinesis, remained substantially preserved.