Charcot–Marie–Tooth disease type 1A (CMT1A) is associated with a DNA duplication at chromosome 17p11.2. In view of the point mutation in the gene for peripheral myelin protein pmp–22/gas–3 in Trembler mice, a murine model for CMT1A, we have analysed whether this gene is altered in CMT1A. Here we show that the human homologue of the murine pmp–22 gene is located within the CMT1A DNA duplication, which is a direct repeat and does not interrupt the coding region of PMP–22. Expression of PMP–22 in CMT1A fibroblasts is similar to expression in control fibroblasts. Increased gene dosage or altered PMP–22 expression in the peripheral nervous system are therefore possible mechanisms by which PMP–22 is involved in CMT1A.