Aim: The study was designed to assess (1) the time course of catecholaminergic activation in acute myocardial infarction (AMI) as estimated by adrenaline (ADR) and noradrenaline (NOR) concentrations, and (2) to relate activation of these hormones to predict the outcome of cardiac performance. Patients and Methods: Eighteen patients with first AMI were studied. Blood samples were drawn within the first 4–18 h, after 18–24 h, on day 2, day 3 and on day 6 as well as after 1 year. Radionuclide ventriculography was performed on the day of discharge and after 1 year to determine left-ventricular ejection fraction (LVEF). Results: In the study group as a whole, the concentrations of ADR decreased from (mean ± SEM) 0.80 ± 0.12 nmol/l on admission to 0.33 ± 0.03 nmol/l at discharge (p < 0.05). NOR decreased from 4.19 ± 0.78 to 2.44 ± 0.33 nmol/l (p < 0.05). Initial peak concentrations of both ADR and NOR on admission were correlated to LVEF at discharge (r = –0.56, p < 0.05 and r = –0.72, p < 0.05, respectively). If NOR was normal (<3 nmol/l) at admission, the LVEF was normal or almost normal (= 0.46) at discharge. The mean plasma level of ADR and NOR after 1 year follow-up was 0.34 ± 0.04 and 1.95 ± 0.25 nmol/l, respectively. The values after 1 year were unchanged compared to values at discharge, at day 6 (n.s.). Mean LVEF was 0.50 ± 0.03 (range: 0.23–0.69) at discharge and unchanged 0.46 ± 0.05 (range: 0.18–0.72) at 1 year follow-up (n.s.). During hospitalisation, the group with LVEF <0.50 had an 86% higher initial ADR and an 82% higher initial NOR concentration compared to values in patients with LVEF >0.50 (p < 0.05). Conclusion: (1) Catecholaminergic activation, as measured by plasma ADR and NOR in AMI, is acute and restricted to the first 5 days. Thereafter, the hormone levels are normal and stable. (2) The magnitude of the early catecholaminergic activation correlates with left ventricular systolic performance. (3) Normal NOR values at admittance predicts normal or almost normal LVEF at discharge.