Surgical Risk Prediction with the POSSUM Score Family R package possum version 0.1.0 Computes the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM), its Portsmouth modification (P-POSSUM), and the colorectal (CR-POSSUM), vascular (V-POSSUM) and ruptured aortic aneurysm (RAAA-POSSUM) variants, risk-adjustment systems used in surgical audit. Functions map physiological and operative variables to their component scores and return the predicted probabilities of morbidity and mortality from the published logistic equations. The coefficients follow Copeland and others (1991) <doi:10.1002/bjs.1800780327> for POSSUM, Prytherch and others (1998) <doi:10.1046/j.1365-2168.1998.00840.x> for P-POSSUM, Tekkis and others (2004) <doi:10.1002/bjs.4430> for the colorectal variant (CR-POSSUM), and Neary and others (2003) <doi:10.1002/bjs.4041> for the vascular variant (V-POSSUM). The package is intended for audit and research; it is not a validated medical device and must not be used as the sole basis for clinical decisions. Software Imports: stats Suggests: tinytest Christos Longros <chris.longros@gmail.com> Comprehensive R Archive Network (CRAN) Christos Longros [aut, cre] (ORCID: <https://orcid.org/0009-0001-2717-0857>), Daniel Enrique Chourio Barboza [aut] MIT + file LICENSE (https://CRAN.R-project.org/package=possum/LICENSE) 2026-07-28 application/tgz https://CRAN.R-project.org/package=possum doi:10.32614/CRAN.package.possum