This prospective cohort study investigated orofacial pain occurring as a manifestation of vincristine neurotoxicity. Forty cancer patients (28 to 63 years of age) receiving vincristine were given baseline interviews and orofacial examinations, which were repeated weekly for 7 weeks of treatment. Twenty-two patients (55%) had neurotoxicity manifesting as orofacial pain. Onset was usually 3 days after vincristine administration; mean duration was 2 days. Twenty patients (50%) were affected in the first week: nine (22%) with severe and five (12%) with moderate pain. Symptoms were mild and infrequent in subsequent weeks. Eighteen control patients receiving chemotherapy without vincristine had no comparable orofacial symptoms. Multiple sites in the distribution of the trigeminal and glossopharyngeal nerves were affected: primarily the temporomandibular joint, mandible, throat, ears, and mandibular teeth. The frequency of orofacial pain increased with younger age. Pain was significantly associated with smaller body surface area (p less than 0.05), indicating a dose-related toxicity, and with sociodemographic variables including smoking (p less than 0.05).