The ESS-1 study was designed to evaluate the long-term effects of the angiotensin-converting enzyme inhibitor (ACEI) enalapril (10 mg per day) on cardiopulmonary system of patients with systemic sclerosis (SSc). Exercise testing is used not only for estimation of coronary reserve but also physical capacity--the major determinant of quality of life. In each patient included to the ESS-1 study we performed ECG exercise test on treadmill (5 times at intervals of 3 months). The first follow-up was completed by 41 patients (23 patients in enalapril group and 18 in placebo group). The exercise duration in the placebo group was 683 +/- 295 sec and in enalapril group 768 +/- 173 sec. After 3 months of study there were no significant differences in both groups (758 +/- 271 sec and 720 +/- 191 sec respectively). The analysis of ST segment deviation did not provide any significant changes after 3 months of treatment. We conclude that 3 months enalapril treatment did not improve exercise tolerance in patients with systemic sclerosis.