Imperatae Rhizoma is in use in oriental medicine. Oriental medical doctors use Imperatae Rhizoma for clearing away blood heat(凉血) and stopping of bleeding(止血), etc. We investigated toxicity, poisoning symptoms or side effects, poisoning treatment and prevention against poisoning of Imperatae Rhizoma. The results were summarized as follows: 1. Imperatae Rhizoma has no toxicity. But, side effects after taking Imperatae Rhizoma occasionally occurred, and they are dizziness, nausea, and increasing frequency of excrements, etc. 2. In order to prevent against poisoning of Imperatae Rhizoma, the patients should keep usage, dosage and notes.