Laryngeal carcinomas are preceded by precancerous lesions in about 20% of cases. The macroscopical appearance of these lesions is not enough characteristic to define their malignant potential. The accurate identification of epithelial abnormalities of the laryngeal mucosa requires biopsy and microscopic evaluation. There are many histological classifications of laryngeal precancerous lesions used at present. Many of them are highly subjective and have low reproducibility. Moreover, the different grades of these classifications not always give distinct guidelines for clinician concerning the treatment modality. The Ljubljana classification seems to be easier, more readily applied and more reproducible. It uses the name "epithelial hyperplastic laryngeal lesion" (EHLL) which includes all alterations in laryngeal squamous epithelium. The four grades of EHLL are: 1. simple hyperplasia (thickening of epithelium due to augmentation of normal prickle cells), 2. abnormal hyperplasia (with increase of basal-like cells), 3. atypical, or risky hyperplasia (epithelium thickened by increase of basal-like cells with pronounced atypical features), and 4. carcinoma in situ (i.e. full thickness change with the features of malignancy but without stromal invasion). The criteria of Ljubljana classification are precise and gives a possibility to make a more clear-cut separation of cases with risk of developing carcinoma from those without it.