The differences in the clinical and diagnostic characteristics of 33 consecutive traumatic unilateral (21 patients, 62%) and bilateral (12 patients, 38%) superior oblique palsies were studied. The unilateral palsies had a large hypertropia in primary position, more vertical than torsional diplopia, a compensatory head tilt to obtain fusion, and a positive Bielschowsky head tilt test. In contrast, the bilateral palsies had small hypertropias in primary gaze that alternated on right and left gaze, a large V-pattern esotropia with excyclotorsion that was frequently bilateral, and a compensatory head position with fusion in upgaze. The results of the study indicate that a V-pattern in excess of 25 prism diopters, an excyclotorsion of greater than 10 degrees, or head trauma severe enough to cause loss of consciousness should also signal bilateral involvement. Torsional diplopia was present in only 20% of unilateral palsies vs 75% of bilateral palsies. The Bielschowsky head tilt test was diagnostic in 100% of the patients with unilateral palsy and 83% of the patients with bilateral palsy. It was undiagnostic in the supine position in all patients. Spontaneous resolution occurred in 65% of the unilateral palsies but in only 25% of the bilateral palsies. Surgical correction was successful in relieving persistent symptoms.