Twenty-six patients with multiple sclerosis (MS) received a total of 45 courses of intravenous methylprednisolone daily for seven days, for acute neurological deterioration. Changes in CSF parameters and clinical status following methylprednisolone were determined and first and repeat courses were compared. There were significant reductions in CSF IgG, CSF albumin, serum IgG and serum albumin levels and CSF IgG synthesis rate in the first and repeat treatment groups. CSF IgG index fell significantly with initial methylprednisolone treatment but not with subsequent courses. Oligoclonal bands disappeared in three patients. Definite clinical improvement followed 30 methylprednisolone courses, possible improvement followed six and no change followed seven. Clinical response was not predicted by pre-treatment CSF IgG synthesis status and did not correlate with its degree of reduction.