Patients with unilateral congenital ptosis often adopt chin elevation to maintain fusion. This compensatory head posturing has been considered a sign of fusion, thus indicating a low risk for amblyopia. To evaluate this sign, we reviewed the charts of 11 preverbal children with unilateral congenital ptosis who had straight eyes and appropriate compensatory head posturing to maintain binocular vision. Four additional patients with unilateral ptosis and no compensatory head posturing were tested for comparison. All patients had undergone an examination and had been tested by pattern Visual Evoked Potential (VEP) under chloral hydrate sedation. Five of the 11 patients with compensatory head posturing were found to be amblyopic, three moderately so and two severely affected. The four patients without compensatory head posturing were amblyopic. It is our hypothesis that compensatory head posturing allows peripheral fusion even when significant amblyopia is present. Additionally, the clinical sign of a compensatory head turn to maintain binocular vision does not rule out the presence of significant amblyopia.