Local hypothermia as a procedure for myocardial protection was utilized in 50 patients; 17 had congenital and 33 aquired heart disease. On patient with diagnosis of A-V canal, previously operated on, died on the 2nd postoperative day after mitral valve replacement and closure of a residual defect. Two other valvular patients died suddenly on the 9th and 20th postoperative days from thrombosis of the prosthesis. The lengths of time of aortic clamping required for correction of these various cardiopathies were analized and correlated with the final results. In comparison with the experience of other authors, a close relationship between the duration of the myocardial ischemia and the figures of morbi-mortality was observed. It is concluded that local hypothermia constitutes an adequate procedure for myocardial protection on the condition that the length of aortic clamping times do not exceed certain limits.