Until recently no simple specific test existed for the differentiation of decompensated heart failure from other causes of acute dyspnoea, or to assess the prognosis of patients with severe heart failure or to optimize heart failure therapy in an individual patient. Measurement of B-type natriuretic peptide has become available as an easy-to-per-form bedside test. Several studies have demonstrated it's usefulness in the emergency room to differentiate heart failure from other causes of acute dyspnoea or to guide the complex drug therapy in an individual patient with heart failure. This article gives a short overview on the clinical experience to use BNP-blood levels for the diagnosis and treatment guidance of heart failure.