In 270 patients with superior oblique paralyses treated between 1973 and 1984, congenital and traumatic causes were most frequent, and one fourth of all traumatic cases had bilateral involvement. Among the diagnostic features distinguishing bilateral from unilateral paralysis were a right hypertropia in left gaze and left hypertropia in right gaze, and a positive Bielschowsky test on tilting the head toward either shoulder. However, absence of either sign did not exclude bilateral paralysis. Large excyclotropia and a V-pattern esotropia are suggestive of but not diagnostic for bilateral paralysis. Complaints about cyclotropia are limited to acquired paralysis. Cyclotropia in the normal eye, head tilt toward the involved side, or absence of any abnormal head posture limits the diagnostic value of these associated signs. Overshoot of the contralateral superior oblique occurred in 19% of the patients and is thought to be caused by contracture of the ipsilateral superior rectus muscle. Surgical treatment in 112 patients resulted in an 85% cure rate with an average of 1.45 operations per patient.