Chronic demyelinating inflammatory polineuropathy (CIDP) is a disease which was recognized several years ago. However, the mechanism underlying its pathogenesis remains poorly understood. Nevertheless, there are some clues which strongly suggest that it constitutes an autoimmune disease. Since 1992 we have studied 30 cases. All them were clinically assessed and submitted to laboratory investigations encompassing nerve conduction studies, sera proteins immunoelectrophoresis, spinal fluid analysis and sural nerve biopsies. Upon clinical examination the usual findings were weakness, muscle atrophy, absence or diminished tendon jerks, paresthesias and hyposthesias. Electrophysiological studies disclosed marked slowing of the nerve conduction velocities, suggesting demyelination. Sera immunoelectrophoresis detected monoclonal gammopathy in 17% of the studied patients, which was not associated with lymphoproliferative illnesses. Of the patients 79% had increased levels of spinal fluid proteins. Seventeen patients gave their consent for performing a sural nerve biopsy; all the samples showed demyelination. In conclusion, we think that CDIP is a disease which can be recognized when the clinical assessment, the nerve conduction studies and the spinal fluid findings suggest the diagnosis. Although nerve biopsy may be strongly supporting, we believe that it has to be performed only if doubts arise from the clinical, electrophysiological or spinal fluid observations. It is worth noting that its early detection may benefit the patient through the administration of the right therapy precluding the eventual sequelae of the disease.