Oral brush biopsy results were compared with scalpel biopsy and histology to determine the positive predictive value of an abnormal brush biopsy finding. Of 243 patients with abnormal brush biopsies, 93 proved positive for dysplasia (79) or carcinoma (14) and 150 were negative for either dysplasia or carcinoma. Therefore, the positive predictive value of an abnormal brush biopsy was 38% (93/243). By using the oral brush biopsy, dentists can inform their patients that abnormal findings have a strong positive predictive value for dysplasia or carcinoma and therefore require follow-up confirmation by scalpel biopsy.