BACKGROUND: The use of anthracyclines in treatment of cancer is limited by cardiotoxicity of these compounds and may lead to heart failure. Therefore monitoring of cardiac function is necessary during therapy. AIM: We evaluated the value of natriuretic peptides (N-terminal pro-atrial natriuretic peptide (N-ANP) and brain natriuretic peptide (BNP)) for monitoring and predicting anthracycline induced cardiotoxicity using radionuclide left ventricular ejection fraction (EF) measurements as reference. METHODS AND RESULTS: A total of 107 consecutive patients receiving anthracycline as part of their chemotherapy for malignant disease were studied. Plasma concentrations of the peptides were measured by radioimmunoassay and EF by radionuclide cardiography. For reduced EF values, i.e. below 0.50 a fairly strong correlation was found between N-ANP or BNP and EF. Of 48 patients with serial EF and peptide measurements, 19% showed a significant EF decrease (>0.10) and ended with a final EF value below 0.50. Baseline EF was no predictor of a change in EF during treatment. Neither baseline levels of N-ANP or BNP nor a change in the same variables during therapy were predictive of a change in EF. CONCLUSIONS: In spite of correlations between peptide concentrations and reduced EF values neither baseline values nor serial measurements can safely substitute EF monitoring in patients undergoing anthracycline therapy.