We report the clinical, electrophysiological, and pathological findings of two unrelated Japanese families with hereditary neuropathy with liability to pressure palsies (HNPP) and confirm the findings of a deletion of peripheral myelin protein-22 (PMP-22) gene. Electrophysiological studies revealed slowing of nerve conduction velocities of the affected nerves. Sural nerve biopsy revealed regions of myelin duplication. The copy numbers of PMP-22 gene was lower than that of normal control, suggesting deletion of 17p11.2 including PMP-22 gene. Our results indicate that HNPP in these two Japanese families is attributable to deletion of 17p11.2 including PMP-22 gene.