Seventeen children were demonstrated to have completely asymptomatic overaction of one or both inferior oblique muscles. None had a constant vertical deviation in primary position, up gaze or down gaze, and significant patterns were absent. None had diplopia or complaints of torsion. The Bielschowsky head tilt test gave a negative result in all cases. No patient showed excyclorotation on fundus examination. Long-term follow-up (28 to 134 [average 75.6] months) of 13 of the patients showed that the condition did not worsen with time and may not require surgical weakening of the inferior oblique muscle.