Postoperative delirium, morbidity, and mortality in our elderly patients with secondary perionitis of colorectal origin is described. This is a chart-based retrospective analysis of 63 patients who were operated on at the University Hospital Basel from April 2001 to May 2004. Postoperative delirium occurred in 33%. Overall morbidity was 71.4%. Surgery-related morbidity was 43.4%. Mortality was 14.4%. There was no statistical significance between delirium, morbidity and mortality (P = 0.279 and P = 0.364). There was no statistically significant correlation between the analyzed scores (American Society of Anesthesiologists classification, Mannheimer Peritonitis Index, Acute Physiology and Chronic Health Evaluation score II, physiological and operative surgical severity and enumeration of morbidity and mortality score' or short 'cr-POSSUM') and postoperative delirium, morbidity or mortality. Postoperative delirium occurred in one-third of the patients, who seem to have a trend to higher morbidity. Even if the different scores already had proven to be predictive in terms of morbidity and mortality, they do not help the risk stratification of postoperative delirium, morbidity, or mortality in our collective population.