Chronic inflammatory demyelinating polyradiculoneuropathy is a paralytic syndrome, causing considerable disability and even death. In controlled clinical trials, plasma exchange prevented or ameliorated neurological deficits, but the efficacy of immune globulin infusion remains unproved. Also unknown is whether immune globulin infusion is as effective, or more effective, than plasma exchange and what dosages and frequencies are best. In this observer-blinded study, using some objective end points not subject to bias (e.g., summated compound muscle action potential), 20 patients with progressive or static polyneuropathy were randomly assigned to receive either of the two treatments for 6 weeks, followed by a washout period, and then were assigned to receive the other treatment. Plasma exchange (twice a week for 3 weeks then once a week for 3 weeks) and immune globulin infusion (0.4 gm/kg once a week for 3 weeks, then 0.2 gm/kg once a week for the next 3 weeks) were used. End points assessed before and after treatment schedules were neurological disability score; muscle weakness of the neurological disability score; summated compound muscle action potentials of ulnar, median, and peroneal nerves; summated sensory nerve action potentials of ulnar and sural nerves; and vibratory detection threshold of the great toe using CASE IV. Observers were masked as to treatment used. Of 20 patients, 13 received both treatments whereas 4 did not worsen sufficiently to receive the second treatment--1 patient left the study during and 2 after the first treatment to receive unscheduled treatment elsewhere.(ABSTRACT TRUNCATED AT 250 WORDS)