We compared the incidence of heart failure (CHF), CHF mortality and CHF severity in cancer patients (pts) treated with doxorubicin (DXR) in the presence and absence of cardiologic monitoring (CM). CM consisted of endomyocardial biopsy and right heart catheterization as definitive tests with and without echocardiograms and phonocardiographically derived systolic time intervals as screening tests. CHF incidence was very low (0.03) in non-CM pts without risk factors (RF). RF pts had a CHF incidence of 0.17 without and 0.06 with CM (P = 0.107). Five of 58 RF pts in the non-CM group and 0 of 49 RF pts in the CM group died of problems related to CHF. CHF symptomatology by NYHA criteria was less in CM RF pts than non-CM RF pts (P = 0.034). The prevention of CHF mortality and morbidity in CM pts was not due to administering less DXR, as CM pts actually received an average of 43 mg/m2 more DXR than non-CM pts. We conclude that pts without RF need no CM during treatment with DXR, and that CM can reduce CHF severity and CHF mortality in RF pts.