Regional anesthesia, an attractive choice of anesthesia for the patients with systemic illness such as pulmonary/heart diseases or endocrine dysfunctions, is generally accepted as a safe anesthetic method. However, there are various kinds of complication annoying the physician and the patient following a regional anesthesia. Therefore, physicians and patients must understand the risks in addition to the benefits of regional anesthesia to make an informed consent of anesthetic technique. 1) This review will give an overview of delayed complications following a regional anesthesia.