UNDOUBTEDLY a major factor in success or failure in peripheral arterial embolectomy has been the time elapsing between the occurrence of the embolism and surgery. There is no uniform agreement on the limits of the optimum period for embolectomy. McClure and Harkins1 set the first 12 hours as the optimum period. Heanley2 would have the surgery done in the first 10 hours. Pearse,3 in reviewing 282 embolectomies, found little difference between the results of those done in the first and those done in the second five-hour periods. The combined average of successful operations in these two periods was 40. The average of the second 10-hour period was 14%, and of the third was 8%. He concluded that after 48 hours the operation was not worth doing. He attributes failure to ( 1 ) the formation of a thrombus distal to the embolus, so-called "tail thrombus," and (2) changes in