Of a series of 16 cases with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) 14 patients were treated with high-dose steroid therapy (HDST, 1.0-1.5 mg/kg/day of prednisone). The average functional disability score (FDS) before treatment was 3.06 +/- 0.11 (maximum FDS = 4). There was a significant improvement under this treatment (FDS = 1.43 +/- 1.12, p less than 0.001). Maximal improvement appeared in 10 patients after 4 weeks of HDST. Following improvement, repeated attempts were made to taper off HDST in 9 patients, 8 of them developed 26 relapses. In most of the patients medium-dose steroid therapy (MDST) with 0.5-0.75 mg/kg/day of prednisone was continued, sometimes with addition of other immunosuppressive medication. The duration of HDST + MDST was between 0.5 and 6.0 years (average 2.6). The following factors were found to correlate with better response to HDST: shorter duration of CIDP, milder neurological deficit, milder decrease of nerve conduction velocity, younger age and being female. Global distribution of weakness, muscle atrophy and a positive Babinski sign were predictive of poor prognosis. Involvement of cranial nerves and level of protein in the cerebrospinal fluid did not correlate with the results of HDST. The risk of relapse was higher with shorter periods of HDST and with more rapid tapering off of HDST. The results indicate that treatment with HDST should be initiated as early as possible, a period of stability of remission is needed before tapering off, and lowering of HDST must be very gradual.