Malignant neoplasm preferentially occurs in the elderly. Common cancers in the elderly are gastric, colorectal, lung and prostate cancers in men whereas colorectal, lung, gastric and pancreatic cancers in women. There are several characteristic features such as tumor location, histology, biological behavior and pathway of carcinogenesis in malignant neoplasms occurring in the elderly. Multiple cancers increase with aging. Although it is generally believed that carcinoma in the elderly shows well differentiation, slow growth, low incidence of metastasis and favorable prognosis, the tumor does not always show such features. Regarding biological behavior of malignant tumor in the elderly, age-related alterations of the host such as stromal weakness and decreased immune response against cancer cell invasion should be considered as well as characteristics of tumor cell itself. Thus, we need a specific strategy for treatment for malignant neoplasms in the elderly.