Randomized clinical trails have demonstrated that angiotensin-converting enzyme (ACE) inhibitors reduce mortality, improve symptoms, and decrease hospitalization rates in congestive heart failure (CHF) patients with impaired left ventricular systolic function. Guidelines from the Agency for Healthcare Policy and Research (AHCPR) endorse the use of ACE inhibitors in eligible CHF patients and note their underutilization in practice. Randomly selected records of 1,212 Medicare CHF patients in Louisiana, discharged between July 1993 and October 1993, were reviewed. Abstracted data were used to characterize practice patterns and pertinent clinical factors influencing current ACE inhibitor utilization by practicing physicians in eligible Medicare CHF patients admitted to acute care hospitals. A total of 1,133 patients admitted were discharged alive; mean age was 77.6 years (64% female; 68% white). One third of the patients (34%) were already receiving ACE inhibitors on admission; of these, 85% were discharged on ACE inhibitors. The remaining 66% of patients were not on an ACE inhibitor on admission; only 35% of these are documented to have been placed on an ACE inhibitor(s) at discharge. Overall, a significantly large number of CHF patient charts (48%) lacked documentation of LV systolic function assessments. On multivariate logistic regression modeling, the following key clinical variables were positively related to the prescription of ACE inhibitors: low ejection fraction, dyspnea and orthopnea, normal creatinine levels, high diastolic blood pressure, cardiomegaly, and increasing age. Among patients with low ejection fraction, factors contributing to not being discharged on ACE inhibitors included: high creatinine levels, history of myocardial infarction or ischemic heart disease, renal failure, and being African American. This study documents the underutilization of ACE inhibitors in patients with impaired left ventricular systolic function. Results suggest the need for increased physician-based educational efforts concerning the use of ACE inhibitors in CHF patients, and also for increasing left ventricular systolic function assessments and documentation of findings in patient charts.