In morphologically diagnosing cancer, pathologists' attention is focussed on the presence or absence of atypia, i.e., the form of cells and tissues deviated from the norm, and if it is present, on its grade. However, due to retarded development of techniques for the objective evaluation of its grade, separation of cancer from premalignant lesions still meets great ambiguity. Particularly, the boundaries of "dysplasia" with cancer and noncancerous lesions are not defined in clear morphological terms and are susceptible to a strong between-observers fluctuation. In this paper we outlined our recent efforts to establish in various organs a statistically most adequate, and therefore reproducible, classification of atypical lesions, resorting to morphometry and multivariate analysis. Two examples were given: atypia of the pancreatic duct epithelia as an object for the study of purely cellular abnormalities, and hepatocellular carcinoma, which required also to quantify the atypia of tissue structures, The classifications thus established proved to be the most adequate, in that, they closely reflected the grade of malignancy in a clinical as well as biological sense, as shown by the clear between-categorier differences in oncogene mutation, DNA ploidy pattern, the patients' prognoses, and so on.