Although the long-term cardiotoxic effects of cumulative doses of doxorubicin are well established, the short-term effects on cardiac function are uncertain. Therefore we examined the short-term effects of doxorubicin on left ventricular systolic and diastolic function following a total of 56 doses of doxorubicin in 15 patients with normal resting left ventricular function. Resting radionuclide ventriculography was performed 1 hour before and 4 hours after each dose of doxorubicin. Left ventricular ejection fraction increased significantly from 64 +/- 1% to 67 +/- 1% (p less than 0.001) after doxorubicin. In addition, peak ejection rate (p less than 0.005) and peak filling rate (p less than 0.0005) increased significantly following short-term doxorubicin administration. There was no relationship between either the individual or cumulative dose of doxorubicin and the acute ejection fraction, peak ejection rate, or peak filling rate response. Our data suggest that doxorubicin acutely increases left ventricular systolic and diastolic function.