OBJECTIVE: To assess how well primary care clinicians select patients needing early referral to a dentist based on an oral cavity examination. DESIGN: Prospective comparison of the screening oral cavity examinations performed by primary care clinicians with that performed by a dentist. SETTING: General medicine clinic and dental clinic of a Veterans Affairs Medical Center. PATIENTS: A sample of 86 consecutive patients attending regularly scheduled appointments in a primary care medical clinic. MEASURES: Each patient was examined independently by two primary care clinicians and then one dentist. History and physical findings, clinical impression, and plan based on the oral cavity examination were recorded. The reference standard was the examination by a dentist blinded to the patient's history. RESULTS: The prevalences of lesions suspicious for premalignancy, periodontal disease, calculus, and caries were 23%, 37%, 54%, and 18%, respectively. When the primary care clinicians noticed a lesion suspicious for premalignancy, the likelihood that such a lesion was present increased significantly (LR+ = 2.7 to 6.6). However, a normal examination by the primary care clinicians did not significantly lower the likelihood of a premalignant lesion (LR- = 0.7 to 0.8). The primary care clinicians were more efficient at evaluating dental and gingival conditions (LR+ = 2.7 to 5.8, LR- = 0.2 to 0.7). CONCLUSIONS: Screening for oral disease by primary care clinicians is justified but should not replace routine screening by dentists.