The aim of this study was to clarify the risk factors of severe postoperative complications and prognostic factors in patients who underwent emergent surgery for colorectal cancer perforation. ASA-PSB3 and Mannheim Prognostic Index(MPI)B27 were selected as the independent risk factors for postoperative severe complications on multivariate analysis. Moreover, severe postoperative complications and non-curative surgery were selected as the independent factors of poor prognosis.