Charcot-Marie-Tooth (CMT) type-1 (CMT1) neuropathy is characterized by peripheral nerve demyelination and has been divided into several subtypes. The most frequent among these, subtype 1A, is related to a microduplication of the region p11.2 of chromosome 17. This region contains the PMP-22 gene which is involved in peripheral nerve myelination. Since motor nerve conduction velocity (MNCV) is closely related to nerve myelination, we compared type-1A patient MNCVs versus non-A CMT1 patient MNCVs, in 57 CMT1A patients and 21 non-A type-1 patients. Patients with the 17p11.2 duplication have MNCVs that are significantly more reduced (about 20 m/s) compared to patients without the 17p11.2 duplication (about 30 m/s). This study also permits a model of the MNCV in the median nerve (MedMNCV) of CMT1 patients, with age, gender and molecular status as parameters. Furthermore, in order to help clinicians to diagnose subtypes of CMT1 patients, the probability for type 1A is modeled as a function of MedMNCV only.