This study was carried out to evaluate the diagnostic utility of autofluorescence photography for oral mucosal lesions. The materials consisted of 15 chemically-induced lesions containing carcinomas in 15 hamsters, and 32 oral lesions in 30 patients. In the animal models, orange fluorescence was detected in all squamous cell carcinomas invading the muscle layer, and the intensity of the fluorescence increased with the progress of the lesions. In the clinical application, orange fluorescence was detected in 14 of 16 malignant tumors and in one of 16 benign lesions. These results suggest that fluorescence photography may be useful for the diagnosis of oral cancer, particularly for squamous cell carcinoma.