The classification and grading of the noninvasive, intraepithelial neoplasms of the urothelium are based on the morphological pattern of growth, i.e., papillary and flat (and endophytic), and on their degree of architectural and cytologic abnormalities. Recent advances in the morphological, molecular and quantitative evaluation of these lesions have contributed to the refinement of the current classification and grading schemes. However, some controversies on the precise criteria and terminology, especially when the papillary lesions are concerned, are still present.