A review was made of 82 consecutive patients undergoing peripheral arterial embolectomy in the 15-year period 1948 to 1963 at the Peter Bent Brigham Hospital, with emphasis on the etiology and histology of the embolism. Rheumatic and arteriosclerotic heart disease comprised the most common causes. In-hospital mortality for patients with rheumatic heart disease was 25% (12 of 45), while that of patients with arteriosclerosis was 75% (23 of 31). Long-term mortality trends showed similar patterns. Aortoiliac arteriosclerosis is the most common cause of embolism of unusual origin. Careful gross and microscopic examination of an embolus may be most helpful in elucidating etiology.