Tissue specimens submitted to an oral pathology biopsy service during a 17 1/2-year period were studied to determine the types of diagnoses rendered, the general types of pathological processes represented, and the epidemiologic distribution of patients. A total of 15,783 cases were studied. Normal structures were observed in 480 cases, mostly dental follicles, and were eliminated from the study. The remaining 15,303 cases had been diagnosed as pathological entities. A majority of the oral biopsies were taken from either infectious or reactive conditions. Fibromas, periapical granulomas, periodontitis, mucoceles, and radicular cysts were the most frequently encountered lesions. Neoplasms constituted nearly 15% of all the specimens, with approximately 18% of these being malignant. An additional 360 lesions (2.4% of the total number of specimens) harbored dysplasia and might be considered premalignant. The peak age groups represented in these patients were the third through sixth decades of life. More oral biopsies were performed on females than males. A majority of the patients were white. The purpose of this study was to determine the relative frequency of oral lesions that were considered to be of sufficient clinical significance to merit a biopsy. Although this data might be used as a guide for forming clinical impressions about oral lesions, the clinician must always be aware of the possible occurrence of more rare lesions.