The review of international classification of tumors of digestive tract is presented: that of Padua (1998), Wien (1998, 2002), WHO (2000). Principal definitions are considered, the content of terms "dysplastic" and "neoplasia" is analysed. The attempt to systematize the description of morphological picture of neoplasia (adenoma/dysplasia) of low and high degree and difference of uncertain neoplastic (dysplasia) from true neoplastic changes. Principles of clinical interpretation of biopsies are presented.