Taxol is a novel antineoplastic agent that has demonstrated impressive clinical activity in breast, ovarian, lung, and head and neck cancers. This broad antitumor activity of taxol in cisplatin-sensitive tumors suggests that the combination of taxol and cisplatin may become one of the most commonly used taxol-based chemotherapeutic regimen in the treatment of solid tumors. Both taxol and cisplatin, however, are neurotoxic. To study the neurotoxic effects of these two agents when used in combination, we prospectively evaluated neurological function at baseline, during, and following treatment, in 21 cancer patients treated with taxol (135-350 mg/m2), cisplatin (75-100 mg/m2), and granulocyte-colony stimulating factor (5 micrograms/kg). Twenty of the 21 patients (95%) developed a sensory-motor neuropathy 1 to 21 weeks after the initiation of therapy, that was progressive with each additional course of chemotherapy. The neuropathy was symmetrical, length dependent, axonal in nature by physiological studies, and more pronounced in those patients who received higher doses of taxol. The neuropathy appeared earlier and at lower taxol doses in those patients with preexisting neuropathies. We conclude that sensory-motor neuropathy is a frequent dose-dependent toxicity of combined cisplatin and taxol use. Peripheral neuropathy is likely to become the major dose-limiting toxicity of taxol-cisplatin combination chemotherapy when higher doses of these agents are administered with granulocyte-colony stimulating factor.