Abstract: A study of nttelealar organizer regions (NOR) inmalignant and benign tumors was performed-with-the method of Ag-staining nucleolar organnizer regions (AgNOR). Results shew that the differences of the numbers of NOR, benigh tumors were compared with slight malignant ones, severe malignant tumors were compared with slight malignant ones, benign tumors and malignant ones were compared with Precancerosis, were significant. The sige and distribution of NOR was different, this. article suggest that NOR counting is very important for differetiating benign tumors from malignant ones, and eveluating biological characters of tumors. Ag-NOR is hepfal new method which may be extensively used in the pathological studies of tumors.