THE EFFECTIVE management of massive pulmonary embolism remains a challenge. The successful treatment rests primarily upon early operative intervention and survival without surgery is extremely low. In the series of sixty-five patients of Hampson, Milne & Small (1961) all but nine died immediately. Donaldson et al. (1963) reviewing 271 cases of massive pulmonary embolism, proved at autopsy, revealed that 30% lived for 30 min, 25% for 1 hr, 15% for 6 hr and only 9% lived for 12 hr. There is a race against time and the character of the circulatory obstruction leaves little opportunity for effective treatment. Unless, therefore, a fast decision is made, only about one in five patients survives long enough for a proper diagnosis and surgical treatment. Although Trendelenburg first proposed pulmonary embolectomy in 1908, Kirschner in 1924 performed the first successful operative procedure. Thereafter within a 7-year period, Crafoord (1928), Meyer (1930) and Nystrom (1930) recorded eight successful cases. Steenberg et al. in 1958 reported the first successful embolectomy in America. In the last few years many more successful embolectomies have been performed at many centres (Beall & Cooley, 1965; Makey & Bliss, 1966; Cross & Mowlem, 1967; Barraclough & Braimbridge, 1967; Paneth, 1967; Sautter, 1967). Among the many factors in the recent increase in success, the most important has been the use of cardiopulmonary bypass, first employed successfully in this context by Sharp in 1962.