A40 -year-old woman visited our hospital with adenocaricinoma of the sigmoid colon with multiple liver metastases and ovarian metastasis. Because of a stenosis of the primary tumor, she underwent a colostomy before chemotherapy. 5-fluorouracil and irinotecan and leucovorin(FOLFIRI)was selected as first-line chemotherapy. At the start of chemotherapy, just after the end of irinotecan and leucovorin administration, the patient developed dysarthria. There were no neurological abnormalities or hematological abnormalities. The treatment was temporarily discontinued, and the dysarthria completely disappeared within 90 minutes. 5-fluorouracil was administered after the disappearance of dysarthria. Within 60 minutes of the administration of irinotecan and leucovorin at the second chemotherapy treatment, the patient developed dysarthria again. The patient had no neurological or hematological abnormalities. Magnetic resonance imaging(MRI)showed no abnormalities. The treatment was stopped and dysarthria disappeared within 60 minutes as it did the first time. At each time, no treatment for dysarthria was performed. This patient refused to continue irinotecan because of dysarthria. Therefore, chemotherapy without irinotecan was continued for the third time onward. In the previous literature, 8 cases of dysarthria caused by irinotecan were reported as a rare toxicity. In all cases, dysarthria was temporary and reversible. Because the mechanism of dysarthria is unclear, specific treatment and precaution for dysarthria is not recommended. Since dysarthria is reversible, however, irinotecan might be continued until progression.