The effect of hyperbaric tetracaine spinal anesthesia was studied in 40 patients having genitourinary surgery in the horizontal lithotomy position. Patients were randomly assigned to one of two groups, after spinal injection, patients in one group were placed immediately in the supine and horizontal lithotomy position, and patients in the second group were placed immediatley in the supine and horizontal position for 10 minutes and then placed into the horizontal 1thotomy position. There were no statistically significant differences in anesthesia sensory level and heart rate of patients placed immediately in the horizontal lithotomy position compared to the patients kept in the supine position for the first 10 minutes after receiving the spinal anesthetic. The ranges of systolic blood pressure were all within normal limits, although systolic blood pressure showed a difference at 5,10 and 60 minute intervals after anesthesia. We conclude that immediate application of the horizontal lithotomy position can be safely practiced in the anesthesia of genitourinary surgery.