Summary Background: Procalcitonin (PCT) is a marker of inflammation in systemic bacterial infections. The aim of this study was to determine the role of PCT as a prognostic marker in cardiovascular intensive care unit (ICU) p atients with non-infectious conditions. Methods: 253 critically ill medical patients were consecutively included during a 4-month period. The highest PCT plasma level during the first 72 hours of ICU stay was taken for analysis, and a level ≥0.5 ng/ml was defined as elevated. Hospital m ortality rates stratified by PCT level were compared among the patients w ithout an infection at ICU admission (n = 223) and among a subgroup of non-infected patients with a cardio vascular diagnosis (n = 164). Results: The non-infected patients with an elevated PCT level had a 38% mortality rate (15/40), whereas a 9% mortality rate was observed among the non-infected patients with a normal PCT (16/183) (p <0.001). The mortality rate was 42% among the subgroup of cardio vascular patients with an elevated PCT level (11/26), whereas it was 4% among the cardiovascular patients with a normal PCT (6/138) (p <0.001). For PCT, the area under the receiver operating characteristic curve for the prediction of mortality was 0.81 (95% confidence interval [CI] 0.74−0.89) in all non-infected patients and 0.90 (95% CI 0.84−0.96) in the cardiovascular subgroup. Conclusions: In apparently non-infected critically ill medical patients, particularly in cardiovascular patients, elevated PCT plasma levels are associated with an increased hospital mortality. Nevertheless, PCT v alues should be interpreted carefully in the clinical context.