Authors conducted a one-year prospective study to determine whether CHOP regimen (cyclophosphamide, doxorubicin, vincristin, and prednisone), used in the treatment of aggressive non-Hodgkin's lymphoma, is associated with the presence of an early impairment of cardiac function. Forty seven patients were prospectively examined (27 male and 20 female) aged 49 +/- 14 years who were treated with CHOP regimen. Rest echocardiography was performed at baseline and one-year control. Cardiopulmonary exercise test was carried out at one-year control examination. The ejection fraction (EF), parameters of diastolic function, myocardial performance index (MPI), and pVO(2) were used as parameters of cardiopulmonary performance. The cumulative dose (CD) of doxorubicin was 277 +/- 56 (300 mg/m(2)) was given. The baseline EF 64 +/- 5% (64%) decreased to 58 +/- 7% (57%) at the one-year control (p<0.0001). 23% of patients exhibited a drop in EF >10% during the follow-up. 43% revealed a pathologically increased value of MPI >0.55, and 47% impaired diastolic function compared to the baseline values, respectively. 21% of patients exhibited a decrease of pVO(2) <20 ml/kg/min, and 17% pVO(2) <80% of the reference value, respectively. None of the patients developed signs of heart failure. The Doppler parameters of both diastolic and global LV function were the most affected measures and significantly influenced the cardiopulmonary performance. Multivariate analysis showed that CD >= 300 mg/m(2) (OR=8.08; p<0.05) and the presence of risk factors (OR=9.48; p<0.008) are the best predictors of cardiotoxicity. The results show that subclinical cardiac impairment was frequent in patients receiving the CHOP regimen with safe cumulative doses of doxorubicin. The value of described changes for the development of heart failure has to be assessed during the prospective follow-up.