BACKGROUND AND AIM OF THE STUDY: At present, no reports are available regarding the hemodynamic assessment and survival of patients undergoing valve replacement with HP-Biplus prostheses. Hence, the present study was designed to acquire this information. The aim was to assess: (i) any potential hemodynamic differences between the HP-Biplus prosthesis and the 'standard' bileaflet mechanical valves (SJM, ATS, Sorin Bicarbon and CarboMedics); and (ii) the incidence of postoperative complications and long-term mortality. METHODS: The data from 242 patients (139 males, 103 females; mean age 58.4 +/- 14.0 years) who survived mitral or aortic valve surgery with mechanical bileaflet standard prostheses (SJM, ATS, Sorin Bicarbon or CarboMedics), between January 1985 and December 2005, were analyzed retrospectively. Evaluations were conducted consecutively with Doppler echocardiography, and compared with 35 patients (20 males, 15 females; mean age 52.2 +/- 12.8 years) who received an HP-Biplus prosthesis and underwent surgery between January 2000 and December 2005. RESULTS: At seven years after surgery, actuarial survival was 40% for the HP-Biplus prosthesis and 84% for the 'standard' prostheses (p < 0.0001). The HP-Biplus prostheses had a higher rate of reoperations for aortic valves (15.2% versus 1.7%; p < 0.003, OR 10.2), a higher rate of prosthesis dysfunction (62.9% versus 7.8%; p < 0.00001, OR 25), and a higher rate of total events (72% versus 21.8%; p < 0.0001, OR 11). CONCLUSION: The present study was the first to compare long-term results of the HP-Biplus prostheses with those obtained with 'standard' mechanical prostheses. Valve replacement with standard prostheses was shown to carry low morbidity and mortality (21.8%), whereas the HP-Biplus prosthesis showed high morbidity and mortality (92%). The data acquired may be very important when selecting prostheses with better hemodynamic characteristics, and show that the HP-Biplus prosthesis, in the authors' opinion, is not suitable for clinical use.