In the present study 19 patients with postanesthetic ulnar nerve lesions treated during the period 1973--76 are reviewed. The lesions were localized to the cubital tunnel region and appeared subsequent to recent, otherwise uncomplicated operative procedures commonly performed under general anesthesia. Mechanical factors caused by malpositioning of the arm during the course of anesthesia and operation resulted in direct, compressive nerve injury. Hypermobility of the nerve was found to be a predisposing local factor. The roentgenologic configuration of the postcondylar groove showed considerable variability and did not correlate with the location of injury. The potential risk positions with the arm in either prolonged extreme elbow flexion or with applied surface pressure over the cubital tunnel region must be avoided in placing the patient on the operating table.