Charcot-Marie-Tooth disease type 1 (CMT 1) is the most common form of the hereditary motor sensory neuropathies (HMSN) with a prevalence in the Italian population of 9.4/100,000 inhabitants. CMT 1 is a genetically heterogeneous disorder. Forty CMT 1 families (35 with recurrence of cases and 5 sporadic cases) living in northeastern Italy were analyzed with the probe pVAW409R3 to reveal the presence of 17p11.2 duplication. The duplication frequency that resulted was about 82% and not significantly different in familial and in sporadic cases (p = 0.801). This kind of molecular analysis can be very useful for the differential diagnosis of CMT 1 and for the early diagnosis in the absence of a clear clinical manifestation.