Three cases of gastrointestinal bleeding observed on the patients with head and neck tumor, who were treated by the combined method, were presented.They were 53-year-old male with advanced squamous cell carcinoma of the mouth floor, 81-year-old female with the gingival carcinoma and 59-year-old male with advanced malignant lymphoma of the paranasal sinus.Two cases died of general weakness caused by the gastrointestinal complication.In the advanced or aged patients of head and neck tumors, special care should be taken for the general condition because complications occur often during the treatment.The effects on gastrointestinal tract during the combined treatment were discussed from the viewpoint of the following items; 1) characteristics of head and neck tumors, 2) an influence of postoperative and emotional stress, 3) after-effects of irradition, 4) side effects of the drugs such as oncolytics or antibiotics or steroid hormones, and 5) the age and general condition of the patient.