Different classifications of epithelial hyperplastic lesions of the larynx were proposed, but none of them has been generally accepted. The basic distinction among these gradings is evaluation of carcinoma in situ as a precancerosis or a distinct and separate entity. In the present study, atypical hyperplasia and carcinoma in situ are evaluated according to the proposed histomorphological criteria of the Kambic-Lenart classification. In an attempt to separate more objectively the histomorphological differences between these 2 lesions, in addition to traditional light microscopical examination, we also performed semiquantitative analysis with statistical evaluation using the Wilcoxon signed rank test. These results revealed a significant morphological and statistical difference comparing atypical hyperplasia and carcinoma in situ on the basis of the following criteria: abnormal mitotic figures (p = 0.005), mitotic activity (p = 0.014), nuclear pleomorphism (p = 0.006), cellular atypia (p = 0.005), dyskeratosis (p = 0.008), and stromal infiltration (p = 0.015). These results confirm our view that atypical hyperplasia and carcinoma in situ are 2 consecutive but different entities in the process of carcinonogenesis.