BACKGROUND Current electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP) are research oriented favoring specificity over sensitivity. Application of such criteria in clinical practice may miss the diagnosis in potentially treatable patients. OBJECTIVES To analyze the electrophysiologic abnormalities in a cohort of patients with clinically defined CIDP, to compare these data with published electrodiagnostic criteria, and to identify a set of abnormalities that is shared by all patients with CIDP. DESIGN Retrospective medical record review. SETTING Academically based neuromuscular clinic. PATIENTS Fifteen patients with clinically diagnosed relapsing sensorimotor CIDP. INTERVENTIONS Administration of intravenous immunoglobulin or prednisone. MAIN OUTCOME MEASURES Electrodiagnostic studies. RESULTS All patients had electrodiagnostic abnormalities in at least 3 nerves with possible partial conduction block or demyelinating range abnormalities in at least 1 nerve. The diagnostic sensitivities of 5 published CIDP criteria were as follows: the Ad Hoc Subcommittee of the American Academy of Neurology AIDS Task Force (40%), Saperstein et al (47%), Nicolas et al (53%), Hughes et al for the Inflammatory Neuropathy Cause and Treatment Group (60%), and Thaisetthawatkul et al (70%). CONCLUSIONS Current electrodiagnostic criteria for CIDP are insensitive and may fail to diagnose the condition in a substantial number of patients. More inclusive criteria that allow identification of patients in routine clinical practice are needed.Arch Neurol. 2003;60:1755-1759-->