The authors report 12 cases of isolated inferior oblique muscle paresis which is very uncommon and mostly of congenital origin, though trauma is also cause. The clinical features, differential diagnosis and treatment of the disease are discussed. Inferior oblique palsy is differentiated from contralateral inferior rectus palsy by Park's 3-step test, and from Brown's syndrome by forced duction test and the overaction of the antagonist superior oblique during version. Surgical procedures include shortening and advancement of the inferior oblique muscle, recession of the contralateral superior rectus and shortening of the contralateral inferior rectus muscle, and tenotomy of the ipsilateral superior oblique.