In a search for early prognostic features in multiple sclerosis, the progression rate was calculated in 200 consecutive multiple sclerosis patients who had had a lumbar puncture, and correlated with age at onset, type of disease course, the patient's sex, as well as with indices of blood-brain barrier breakdown and intrathecal IgG synthesis. The present study demonstrates that age at onset plays a role in determining whether the disease will be remitting-relapsing or chronic progressive. Age at onset is also a factor determining the rate of progression of the remitting-relapsing form, but is without influence on the progression of the chronic progressive form. A chronic progressive disease course per se (independent of age at onset) is also associated with a more rapid deterioration. The patient's sex does not appear to be a differentiating factor. Only inconsistent correlations were found between IgG index or number of oligoclonal bands in the CSF and disease progression.