The diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) relies primarily on clinical and electrophysiologic examination, but the nerve biopsy findings may be supportive, especially in atypical cases. In order to define the usefulness of nerve biopsy in this disease, we retrospectively studied 44 consecutive patients whom we classified as having CIDP on pathological grounds. We found that 8 of these 44 patients had pathological findings indicative of CIDP but did not meet any of the usually accepted electrophysiological criteria for its diagnosis. Among these eight patients, five responded favorably to conventional therapy. All of these eight patients had an electrophysiological pattern of generalized axonopathy with additional subtle findings suggestive of demyelination that prompted us to perform a nerve biopsy. Our data suggest that a significant number of patients with unrecognized CIDP are erroneously classified as having chronic idiopathic axonal polyneuropathy. CIDP should be suspected if the electrophysiological examination displays subtle abnormalities suggestive of demyelination, even in the presence of a prominent axonal pattern. Nerve biopsy in these patients may reveal abnormalities suggestive of CIDP and guide therapeutic options.