We report here a patient who was diagnosed as having acute lymphoblastic leukemia (ALL-L2) and colon carcinoma simultaneously and a successful operation for the colon carcinoma was performed preceded to the treatment of ALL. The patient was a 43-year-old male who presented with acute abdominal symptoms and was diagnosed as ALL by the hematological examination and as colon carcinoma (well differentiated adenocarcinoma, Borrmann II) by colon fiberscope. The patient was underwent sigmoidcolectomy for colon carcinoma and was received antibiotics as well as recombinant human granulocyte colony-stimulating factor (rhG-CSF), Approximately two weeks later, the patient received AdVP (Adriamycin, vincristine, and prednisolone) for ALL and achieved a complete remission. It might be possible for some leukemia patients manifesting acute abdominal symptoms to perform surgical approaches, since the prognosis of leukemia patients improved and supportive therapies, including an application of rh-CSF, have developed.