We analyzed the primary tumors, sonographic findings, clinical manifestations, and prognosis in five cases of isolated splenic metastases to determine in what situations these rare metastases should be suspected. The metastases were detected by ultrasonography in all five patients, and the primary tumors were colonic cancer in four patients and renal cancer in one patient. Splenectomy was performed and the postoperative course was uneventful in all patients. We conclude that preoperative and follow-up examinations must be performed with special attention given to the spleen in colonic or renal cancer patients.