Under hypothermia and extracorporeal circulation 187 cases of open-heart surgery were done between November 1963 and October 1974. The results obtained are summarized as follows. 1. Out of 187 cases, 116 cases were male (62.0%) and 71 cases were female (37. 9%). 2. There were 134 cases (72%) in A.S.D., V.S.D., and T/F, and 70 cases (37%) were under 10 years of age and 154 cases (82%) under 30 year age group. 3. Premedicants were secobarbital (83.8%) and atropine sulphate (27.9%) 4. Induction of anesthesia was mainly by the use of thiopental and succinylcholine after preoxygenation with 100% O2, and anesthesia was maintained by N2O-O2, halothane or methoxyuflrane during maintenance. 5. During by-pass, anesthesia was maintained by hypothermia, muscle relaxants or ketamine. 6. From 1963 to 1966, low flow and moderate hypothermia were used with a Zuhdi-Greer oxygenator and a sigma pump and since then high flow was used, utilizing various bubble oxygenators with a De-Bakey's roller pump. 7. Blood pressure, electrocardiogram (ECG), central venous pressure, respiration, temperature, urine output, hemoglobin, hematocrit, arterial blood gas study, pH, intake, output, and electrolytes were monitored before and during anesthesia. 8. There were 28 fatalities (15%) among 187 cases. Death were mostly from bleeding, renal failure, lung edema, low cardiac output syndrome and complete heart block.