The presence of 17p11.2 duplication in CMT 1 Italian families was studied. Fourteen families were tested with pVAW409R3a probe which detects the duplication at D17S122 locus. The duplication was found in all affected individuals, but not in the unaffected relatives and in the unrelated spouses. Also two sporadic cases were investigated: the duplication was present in both patients confirming this mutation as cause of the disease.