Cytology smears from 325 oral carcinomas were studied; the false-negative rate was 37%. Cancers of the floor of mouth exfoliated most malignant cells and those of the gingiva exofoliated the least. There was no correlation between the histologic grading, location, sex of the patient, and the result of the cytology smear. Oral exfoliative cytology should only be used as an adjunctive measure and is not a substitute for biopsy.