BACKGROUND: Community-acquired pneumonia (CAP) is common and associated with a considerable risk of acute kidney injury (AKI). METHODS: We prospectively enrolled 341 patients presenting to the emergency department with CAP (mean age 72, male 61%). Blinded measurements of three natriuretic peptides (NT-proBNP, MR-proANP and BNP) were performed upon presentation. The primary endpoint was the accuracy of the natriuretic peptides to predict AKI within 48h. RESULTS: AKI occurred in 24 patients (7.6%) within the first 48h. NPs and creatinine were significantly higher in AKI compared with patients without AKI (NT-proBNP 9517 [2042-26,792] vs 1177 [280-4167]pg/ml; MR-proANP 641 [196-1075] vs 182 [99-352]pmol/l; BNP 592 [230-1630] vs 160 [64-463]pg/ml; creatinine 166 [131-289] versus 100 [78-134]μmol/l, P<0.001 for each). Predictive accuracy as quantified by the area under the receiver operating characteristics curve was moderate to high: NT-proBNP 0.79 (95%CI 0.70-0.88), MR-proANP 0.78 (95%CI 0.67-0.88), BNP 0.74 (95%CI 0.63-0.85), creatinine 0.77 (95%CI 0.66-0.88). In multivariate logistic regression analysis, NPs remained the only independent AKI predictors: NT-proBNP (increase of 200pg/ml) OR=1.01, 95%CI 1.00-1.01, P=0.009; MR-proANP (increase of 100pg/ml) OR=1.23, 95%CI 1.09-1.39, P=0.001; BNP (increase of 100pg/ml) OR=1.08, 95%CI 1.03-1.14, P=0.002. CONCLUSIONS: NP levels are significantly elevated in CAP-patients experiencing early AKI. Their potential to predict early AKI is comparable to serum creatinine and might be useful in cases of diagnostic uncertainty.