We studied prospectively 105 unselected patients complaining of ptosis and/or diplopia due to extrinsic ophthalmic muscle palsies without other neurological signs. All patients underwent the same diagnostic protocol. The presenting symptoms were: ptosis, 35 patients (33%); diplopia, 27 patients (26%); ptosis and diplopia, 43 patients (41%). The oculomotor nerve was most frequently involved, followed by the abducens nerve. The final diagnoses were: ocular myasthenia, intracranial and/or orbital pathology, thyroid ophthalmopathy, diabetic ophthalmoplegia, mitochondrial myopathy, oculopharyngeal muscular dystrophy. In 26 patients (25%) the cause remained undetermined. Our study confirms the difficulty of establishing an aetiological diagnosis in patients with isolated ocular palsies.