Las tasas brutas de morbi-mortalidad no son indicadores fiables del resultado del producto sanitario, siendo necesario el uso de escalas de riesgo adjustadas por paciente y gravedad. En nuestro estudio se validaron 5 escalas de riesgo para predecir morbilidad y mortalidad en nuestros pacientes sometidos a cirugía programada (POSSUM, P-POSSUM, SAPS II, APACHE II, MODS y MPM). Tras la validación se aplicaron prospectivamente, demostrándose la utilidad de POSSUM y P-POSSUM para predecir morbilidad y mortalidad, por lo que se recomienda su uso en los servicios quirúrgicos. / the use of raw tases to mesuring health results not only is innacuracy but also is dangerous, due to the fact that, the results in medicine depend on the ability of phisician, phisiological status, pre and postoperative cares and kind of intervention. The aim of our study is the validation and prospective aplication of 6 adjusted risk scores (POSSUM, P-POSSUM, SAPS II, APACHE II, MOD S and MPM). We can draw the following conclusions: POSSUM and P-POSSUM are POSSUM and P-POSSUM systems have a high reliability in application for measuring risk of mortality and morbidity in patients studied. APACHE II, SAPS II and MODS scores do not have good reliability in their application for predicting mortality in surgical patients. The use of the POSSUM and P-POSSUM systems is highly recommended in the surgery services to monitor and detect errors in clinical practice.