BACKGROUND While the use of angiotensin-converting enzyme (ACE) inhibitors for patients with congestive heart failure (CHF) is supported by the results of clinical trials and expert guidelines, national physician practices are unknown. METHODS We analyzed 1529 physician office visits by patients with CHF available from the 1989 through 1994 National Ambulatory Medical Care Surveys. We examined changes over time in the use of ACE inhibitors and use of other medications for CHF. Potential clinical and nonclinical predictors of use of ACE inhibitors were evaluated using multiple logistic regression. RESULTS The prevalence of CHF increased from 0.9% of all office visits in 1989 to 1.1% in 1994. Use of ACE inhibitors increased from 24% in visits by patients with CHF in 1989 to 31% in 1994 (P = .02). From 1989 through 1994, use of ACE inhibitors was more likely in visits to cardiologists (46% vs 22% for all other physicians), in the Midwest (31% vs 24% in all other regions), in whites (27% vs 21% in nonwhites), in privately insured patients (31% vs 24% in all others), and in men (29% vs 23% in women). Multiple logistic regression analysis showed independent effects of specialty, region, and sex. Other medications commonly used for patients with CHF included diuretics (62% of visits for 1989-1994), digoxin (38%), and calcium channel antagonists (15%). Use of diuretics showed no significant trend between 1989 and 1994, whereas use of digoxin decreased significantly. CONCLUSIONS The low rates of use of ACE inhibitors in patients with CHF and the wide variations in their use suggest a need to move beyond clinical trials and focus attention on modifying physician practices.