OBJECTIVES:

I. Assess the efficacy of 3,4-diaminopyridine in patients with stable chronic demyelinating polyneuropathy.

PROTOCOL OUTLINE: This is a randomized, double-blind study. Patients are randomly assigned to oral 3,4-diaminopyridine (3,4-DAP) or placebo administered for 4 days. After a washout of at least 5 days, patients cross to the alternate therapy for 4 days.

PROTOCOL ENTRY CRITERIA:

--Disease Characteristics-- Clinical diagnosis of demyelinating neuropathy, i.e.: Hereditary motor and sensory neuropathy type I Chronic inflammatory demyelinating polyneuropathy meeting American Academy of Neurology AIDS Task Force criteria Multifocal motor neuropathy and conduction block Clinically stable for at least 6 months prior to entry --Prior/Concurrent Therapy-- At least 6 months since change in immunosuppressive dose --Patient Characteristics-- Age: 20 to 80 Hepatic: No predisposition to hepatic disease Renal: No predisposition to renal disease Cardiovascular: No predisposition to cardiac disease Other: No other medical condition affecting neuropathy or study evaluation No predisposition to seizures