The CASSIS study was a double-blind multicentric controlled Czech and Slovak study focused on treatment of chronic heart failure with the ACE inhibitor spirapril; it was conducted for 12 weeks. The present work analyzes the second year of the extended open part of the study when all patients (n = 168) were treated with 3 mg or 6 mg spirapril. A small proportion of the patients was treated with 12 mg spirapril. The objective of the study was to test the long-term effectiveness and tolerance of spirapril. The general mortality was analyzed throughout the whole two-year period. The results revealed an unchanging total mortality, analyzed after three-month intervals, during the whole two-year period. Also the functional improvement of the patients according to NYHA which occurred after the first three months of treatment was preserved during the second year. Spirapril proved to be a well tolerated ACE-inhibitor. The authors did not observe angioneurotic oedema in any of the patients. Hypotension and cough were recorded in 0.6% of the patients. The incidence of undesirable laboratory effects was also low and the majority was due to the basic disease. Creatinine did not rise significantly and a rise of urea was observed only in a small number of patients. Liver functions and haemogram did not change during treatment. The results of the second year of erxtension indicate that spirapril is a very effective and safe ACE-inhibitor which will extend in a significant way therapeutic means in patients with chronic heart failure.