A total of 73 patients with myocardial infarction (MI) were included into a prospective study involving intravenous and/or intracoronary streptokinase administration. The total ejection fraction (EF) and the extent of left ventricular dys- and akinetic areas were measured by contrast ventriculography in the first 3-9 hours and 4 weeks after the onset of MI symptoms. Coronary reperfusion performed in the first 3 hours after the onset of symptoms in patients with anterior MI (n = 8) and following 3-9 hours (mean 6.6 +/- 0.89 hours) in patients with inferior MI (n = 17) significantly (p less than 0.05) reduced the extent of dys- and akinetic areas from 20.5 +/- 4.16 to 6.0 +/- 3.99 and 10.0 +/- 1.56 to 5.0 +/- 1.74%, respectively) following 4 weeks. EF significantly (p less than 0.01) increased in the former and tended to show an increase from 51.0 +/- 2.44 to 64.0 +/- 2.26% (p less than 0.1) in the latter. In patients with anterior MI (n = 19) there was a tendency to a decrease in the extent of dys- and akinetic areas from 26.0 +/- 2.85 to 17.0 +/- 3.9 (p less than 0.1) following 3-9 hours. No substantial changes were observed in the values of left ventricular dys- and akinesis and EF in patients with anterior (n = 13) and inferior (n = 16) MI without coronary reperfusion.