Potential risk factors responsible for development of doxorubicin-induced congestive heart failure were examined through retrospective analysis of 4018 patient records. The overall incidence of drug-induced congestive heart failure was 2.2% (88 cases). The probability of incurring doxorubicin-induced congestive heart failure was related to the total dose of doxorubicin administered. There was a continuum of increasing risk as the cumulative amount of administered drug increased. A weekly dose schedule of doxorubicin was associated with a significantly lower incidence of congestive heart failure than was the usually employed every 3-week schedule. An increase in drug-related congestive heart failure was also seen with advancing patient age. Performance status, sex, race, and tumor type were not risk factors. These data will enable clinicians to better estimate the risk/benefit ratio in individual patients receiving prolonged administration of doxorubicin. They also provide a basis for the investigation of less cardiotoxic anthracycline analogues or for designing measures to prevent doxorubicin-induced cardiomyopathy.