The aim of the study was to assess the influence of cardiac resynchronization therapy(CRT) on a series of humoral parameters crucial for the pathophysiology of chronic heart failure such as aldosterone or the inflammatory markers. Thirty eight consecutive patients (aged 66.3 +/- 9.6 years, 31 men - 82% ) with chronic heart failure (57.9% with ischaemic background and 42.1% of non-ischaemic etiology) in stable for at least 3 months, NYHA class III - IV despite optimized pharmacotherapy, with left ventricular ejection fraction (LVEF) < or = 35% and wide QRS complex (> or = 120 ms) had the blood serum tested for the concentrations of interleukin-6 (IL-6), interleukin-18 (IL-18), C-reactive protein (CRP) and aldosterone before and 12-16 weeks after CRT introduction. In the study group aldosterone concentrations were significantly reduced. Among the inflammatory markers the level of IL-6 decreased, IL-18 concentrations showed a falling trend (445.1 +/- 225.7 pg/ml vs 418.4 +/- 229.6 pg/ml, p = 0.052), whereas no change of CRP serum contain was noted. It was showed that cardiac resynchronization therapy had an impact on systemic inflammation and hormonal status in patients with chronic heart failure during short-term observation.