Cancer of unknown primary site (CUP) is not a rare entity and accounts for 3-5% of all malignant neoplasias. CUPs are diagnosed with metastatic lesion so they are all in the advanced stage. Systemic chemotherapy is applied in many cases, but the ideal therapeutic strategy has not yet been determined. CUP shows much histological and therapeutic heterogeneity. Histologically, half of CUPs are adenocarcinoma and the rest are undifferentiated carcinomas. We analyzed the clinical and therapeutic characteristics 22 cases of CUP patients. Most CUP patients are found from lymph node swelling. There is no significant tendency as to the site of lymph node metastasis. Bone metastases are frequently encountered. It seems undifferentiated carcinomas are more responsive to chemotherapy. Chemo-sensitive patients are likely to have a longer life expectancy. In our experience all of the chemo-responsive cases are treated with platinum-based chemotherapy. Today several platinum-based combination chemotherapies are reported, but there is no large-scale randomized study. Because of its variety, individualized therapy may be ideal for CUP.