The present study is based on a multicenter documentation system which includes standardized information on a total of 1271 patients with multiple sclerosis (MS). In 441 (34.7%) cases the optic nerve was involved at the first appearance of the disease, and in 212 (16.6%) subjects optic neuritis (ON) was the sole initial sign. For all MS patients with ON at the onset of the disease the female to male ratio was 1.3, whereas it was 1.5 for the whole series. The mean age at onset was 2 years lower for patients with initial ON as compared with the whole series (29.0 and 31.1 years, respectively). Correlation of the disability of the patients to the duration of the disease revealed the best prognosis for patients with ON as the sole inital sign of MS. The frequency of brainstem/cerebellar and pyramidal signs was lowest among these patients at the time of the present examination. The difference was more pronounced during the first years of the disease and disappeared after longer duration. The correlation curves of disability to the present age of the patients confirmed this pattern. Our findings do not support the idea of initial ON as being a favorable sign of the later course. As an initial bout of MS, it reflect more precisely the mean age of onset of the disease than other signs.