Diagnosis of the cubital tunnel external compression syndrome, and subsequent avoidance of further external pressure, minimizes the possibility of progressive crippling of the hand. The usual clinical features are local tenderness over the cubital tunnel, often accompanied by distal paresthesias, and neurological deficit in the ulnar nerve distribution with sparing of the flexor digitorum profundus and flexor carpi ulnaris muscles; the elbow flexion test, described by the author, awaits evaluation in the diagnosis of the syndrome. Clinicians and others concerned with positioning patients on the operating room table or caring for patients in the ward should be aware of the syndrome. Avoidance of a position of the elbow which predisposes to external compression of the cubital tunnel is mandatory and active elbow movement should be encouraged in bedridden and chair-bound patients. Surgical treatment is sometimes indicated, at least to halt progression of the palsy. A classification of the cubital tunnel syndrome is proposed: physiological, acute and subacute due to external pressure (both forming the cubital tunnel external compression syndrome) and chronic (space-occupying lesions and loss of volume due to lateral shift of the ulnar as a consequence of childhood injury to the capitular epiphysis). Nerve conduction studies may be helpful in the diagnosis of the doubtful cubital tunnel syndrome, particularly when there is definite impairment of power or sensation in the hand.