An unselected series of 1,000 cases of paralysis of cranial nerves III, IV, and VI was retrospectively analyzed regarding ultimate recovery and final causal diagnosis. The frequency of involvement of the third, fourth, and sixth cranial nerves was relatively unchanged from earlier similar reports. The number of patients (263) whose cranial nerve paralysis was initially of undetermined cause was surprisingly high despite the availability of computerized tomographic scanning. Subsequently, the cause for the paralysis was diagnosed in only ten of the 127 patients who could be traced. About half (51%) of the patients with no known cause for paralysis underwent spontaneous remission. Forty-eight percent of all patients recovered. Cranial nerve impairment due to vascular disease (diabetes mellitus, atherosclerosis, or hypertension) was temporary in 71% of the patients, regardless of the cranial nerve affected. Patients with palsies caused by aneurysm, trauma, and neoplasm was predictably less likely to recover.