The management of patients with isolated oculomotor nerve palsies (OMPs) who have normal pupils and no other signs of neurological disease is a controversial issue. A more precise delineation of the clinical course of isolated OMPs may help to determine whether neuroradiologic evaluation is indicated in these cases. We studied 41 patients with isolated third cranial nerve palsies, emphasizing the times of progression and resolution of the oculomotor nerve dysfunction. The average interval from onset to development of maximal ophthalmoplegia failed to differentiate between a microvascular etiology (3.3 days) or posterior communicating artery aneurysm (3 days). Of the 28 patients with diabetic or idiopathic palsies, regardless of pupillary involvement, 68% had improvement of the oculomotor paresis within 4 weeks, 96% within 8 weeks, and 100% within 12 weeks of the onset of symptoms. Our study suggests that patients with pupil-sparing OMPs should be considered for extensive neuroradiologic evaluation only if there is deterioration or failure to improve within 4 to 8 weeks.