Taxol, a plant alkaloid with promise as an antineoplastic agent, produced a predominantly sensory neuropathy in 16 of 60 patients treated in two phase I trials. This neuropathy occurred only at taxol doses greater than 200 mg/m2. Symptoms typically started 1 to 3 days following treatment, beginning in the hands and feet simultaneously in most patients. Electrophysiologic data suggests both axonal degeneration and demyelination. This previously undefined neurotoxic neuropathy most likely results from taxol's unique ability to produce microtubule aggregation in dorsal root ganglion cells, axons, and Schwann cells.