Colposcopy is an established technique for diagnosis in gynecology. Many premalignant and malignant lesions in these areas have discernible characteristics which can be detected using a colposcope, providing an enlarged view of the areas, allowing the colposcopist to visually distinguish normal from abnormal appearing tissue and take directed biopsies for further pathological examination. The diagnosis of a dysplastic lesion of the oral mucosa cannot be based solely on clinical findings. Therefore, histological evaluation of a representative biopsy specimen is necessary. The site for the biopsy is a subjective choice that sometimes raises doubts about its representativeness. So far, no simple and reliable method is available for selecting the most appropriate area for biopsy. Intraoral microscopy (oral application of the colposcopy technique) of mucosal lesions seems to offer advantages in selecting more representative sites for biopsy than routine clinical examination alone. The biopsy sites identified by direct oral microscopy show more advanced histologic signs than those selected by routine clinical examination. This article enlightens the application of colposcopy in diagnosis of oral premalignant lesions and malignant lesions.