In colorectal surgery, drains are expected to prevent hematoma, fluid collection, or abscess formation, to act as an indicator of postoperative complication, or to minimize the severity of complication-related symptoms. Routine drainage has not been advocated by meta-analyses as they failed to demonstrate any benefit in reducing anastomotic leak rate, minimizing symptoms, or serving as a warning function. Moreover, some reports even showed that drain itself is an independent risk factor of anastomosis. The introduction of total mesorectal excision (TME) for rectal cancer surgery has given further concern to this controversial issue, that the use of drain decreased anastomotic failure rate and the need for surgical re-intervention. While controversy still remains, the choice of using drain is left to the individual surgeon's preference in daily practice. Therefore, surgeons should be well acquainted with purpose of drainage (prophylaxis, information, or treatment), characteristics (materials), clinical application of drain (type of drainage system, timing of removal), surgical outcomes after using drain (incidence of postoperative complication), and drain-related complications. If drains are used, careful observation with proper use is crucial for the management. It is important that the duration of drainage should not be inadequately extended. Any complications directly associated with the use of drain should be avoided. New concepts of drain have been proposed as diagnostic tool using biomarkers, and as preventive device against anastomotic leak. This article overviews the available, published data on the use of drain in colorectal surgery.