From May 1977 to April 1990, 1000 cases of open heart surgery were performed under the cardiopulmonary bypass. There were divided into group A[500 cases, from May 1977 to June 23rd 1986] and group B[500 cases, from June 23rd 1986 to April 1990] which were analyzed, summarized, and compared. Of 1000 cases of open heart surgery, 677 cases[67.7%] were congenital heart diseases, and 323 cases[32.3%] were acquired heart diseases. In 677 cases of congenital heart disease, there were 545 cases with acyanotic congenital heart anomaly[A: 279, B: 266] and 132 cases with cyanotic congenital heart anomaly[A: 87, B: 45]. In 323 cases of acquired heart disease, most cases were valvular heart disease[315 cases, A: 133, B: 182] in which 357 valves were implanted. The operative mortality of congenital R acquired heart disease was 7.8% & 8.0%, and then overall mortality was 7.9%. The operative mortality was markedly decreased. [about half] from 10.0% of A group to 5.6% of B group.