Neurologic improvement with use of prednisone, in some cases on several occasions, was demonstrated in seven patients who had a chronic progressive polyradiculoneuropathy with nerve conduction velocity and electromyographic findings consistent with segmental demyelination and axonal degeneration and increases protein concentration in the cerebrospinal fluid. These patients seemed to have the progressive form of chronic inflammatory-demyelinating polyradiculoneuropathy and, in addition, had clinical features of hereditary motor and sensory neuropathy including pes cavus and hammer toes. On systematic examination, bony abnormalities or asymptomatic neuropathy typical of subclinical inherited neuropathy was discovered among their kin. There patients might therefore be identified as having inflammatory-demyelinating hereditary motor and sensory neuropathy. These cases may represent a chance association of chronic inflammatory-demyelinating polyradiculoneuropathy and hereditary motor and sensory neuropathy, a causally linked association of these disorders, or a prednisone-responsive inherited neuropathy only. We wish to draw attention to this treatable neuropathy and to raise the question of whether environmental factors play role in the expression of dominantly inherited mutant genes.