Although an abundance of short-term clinical trials has evaluated the use of enalapril in congestive heart failure (CHF), there has been a paucity of data regarding the long-term effects of this angiotensin-converting enzyme inhibitor. Moreover, a question has arisen as to whether a once- or twice-daily dosing schedule is preferable. To address these issues, a multicenter trial was conducted with the objective of obtaining long-term (48 weeks) experience with enalapril in 142 patients with CHF. A subgroup of patients (n = 88) were randomized to receive enalapril in a dosing schedule of either 20 mg once daily or 10 mg twice daily. Of the overall group, 96 patients completed the 48 weeks of follow-up. Improvement in New York Heart Association functional class, exercise duration and left ventricular ejection fraction was observed. Improvement in clinical status was seen in 68% of all patients, whereas conditions in 5% worsened with enalapril therapy. The most frequent adverse experiences were dizziness and hypotension. There were no obvious differences between the effects of the once- and twice-daily dosing regimens, with doses of 20 mg/day and 2.5 to 15 mg/day being given to about 70 and 30% of patients, respectively. Enalapril appears to provide well-tolerated and effective long-term therapy for CHF.