We report the clinical, pathological, and genetic findings of 23 patients in 8 families with hereditary motor and sensory neuropathy (proximal dominant form) (HMSN-P) in Okinawa, Japan. The clinical features were unique with respect to autosomal dominant inheritance, Kennedy-Alter-Sung syndrome-like proximal dominant neurogenic atrophy, obvious sensory involvement, painful muscle cramp, fasciculations, areflexia, and high incidences of elevated creatine kinase levels, hyperlipidemia, and diabetes mellitus. Electrophysiological and pathological studies revealed typical motor and sensory axonal neuropathy, and decreased numbers of anterior born and dorsal ganglion cells, which suggested the presence of neuronopathy in HMSN-P. Genetic linkage studies showed a lod score of 4.04 (two-point analysis) in DNA marker D3S1284. Haplotype analysis showed that the gene locus of the disease was mapped to 3p14.1-q13 bracketed by D3S1285 and D3S1281. In this region, the patients' chromosomes showed an obvious increase in the allele frequency of five markers. One allele in D3S1591 was identical in all patients but had a low frequency in the control population. This finding suggested the presence of linkage disequilibrium and a common origin of this allele in all patients with HMSN-P. The HMSN-P described here is a new clinical entity characterized by unique clinical manifestations and a new gene locus.