he influence of the neurohumoral system, as adrenergic system or renin-angiotensin system, on cardiac performance in heart failure is not yet know. In order to evaluate the influence of neurohumoral activation in chronic heart failure we followed 51 patients, 47 males and 4 females of mean age 58 +/- 10 years. They suffered from chronic heart failure of different origin and were classified according to NYHA classification: 42 patients were in class III and 9 were in class II. They were treated with digoxin and diuretics since long time. Ejection fraction (EF) was obtained by RVG at baseline and 8 months later. In order to test the influence of adrenergic system on EF we checked plasmatic norepinephrine levels and we divided the patients in two groups: Group A with high levels of plasmatic norepinephrine (1114 +/- 594 pg/ml) and Group B with normal level (426 +/- 139 pg/ml). Group A showed a reduction of EF (-3.73 +/- 1.27%) while, Group B showed a small increase of EF (+ 2.57 +/- 4.32%). To test the influence of renin-angiotensin system we also evaluated the patients according to the value of plasmatic renin activity: normal or high level. We did not observe a significant difference between the 2 groups. Patients with high plasmatic norepinephrine value presented a significant reduction of EF compared to those with low plasmatic norepinephrine. The adrenergic system seems to be more important than renin-angiotensin system or cardiac performance.