Sixty consecutive patients undergoing lumbar laminotomy or laminectomy underwent preoperative and postoperative compression ultrasonography of the lower extremities to detect acute deep venous thrombosis (DVT). Compression stockings were the only method of prophylaxis. Three patients (5%) developed postoperative calf DVT. Despite continued treatment with only compression stockings, serial scanning failed to detect propagation of the thrombus proximal to the knee in any patient. The average age of patients who developed DVT, 62 years, was significantly greater (P < .05) than the age of patients who did not, 45 years. There were no statistically significant differences in DVT rates when compared by: sex, addition of one- or two-level fusion, length of procedure, or number of days of bedrest.