Fifty consecutive patients with acute myocardial infarction admitted to a coronary care unit within 6 hours from onset of symptoms were randomly assigned either to a treatment group ( n = 27) receiving glucose-insulirr-potassium-albumin (GIKA) or to a control group (n=23), comparable regarding clinical data, receiving 5.5 % glucose. Both infusions were given intravenously at a rate of 1.2 ml/kg b.wt./hour during 48 hours. The GIKA solution contained 40 mEq K+, 10 ml 20% albumin and 16 IU regular crystalline insulin per 1000 ml 10 % glucose. Before the infusion, the treatment group received an i.v. loading dose of 50 ml 50% glucose. Serum time activity curves for creatine kinase (CK) and myoglobin (MG) were established from frequent blood Level determinations. A 15minute single-lead ECG was recorded every fourth hour and subsequently analysed for ventricular arrhythmias. The two patient groups did not differ regarding cumulative MG and CK release. The GIKA group had significantly more patients with high MG/CK ratios (p<0.02). No clinically significant difference was found between the two patient groups regarding ventricular arrhythmias, even if ventricular extrasystoles tended to occur less frequently in the GIKA group.