Between May 1991 and February 1992, 31 consecutive patients were included in a prospective study, the aims of which were to determine the criteria of early coronary revascularisation after intravenous thrombolysis in the acute phase of myocardial infarction. The rise in serum myoglobin, the ST segment elevation, accelerated idioventricular rhythm and the evolution of chest pain were analysed. All patients underwent coronary angiography. Twenty-six were revascularized and 5 remained with coronary occlusion. Two types of serum myoglobin curves were demonstrated. Those with a sudden , decrease and a well defined peak in the first 4 hours were specific for revascularisation and easily identified (Group A: 16 patients). The graphs with a progressively rising slope to a peak after the 4th hour were observed in patients with coronary occlusion, but also in 10 patients with recanalized arteries (Group B). No significant difference was demonstrated with regards to the clinical and coronary angiographic parameters between patients in Group A and Group B. On the other hand, the time between the onset of chest pain and peak myoglobin was shorter in Group A (298 +/- 81 min) than in recanalised patients in Group B (380 +/- 54 min) (p < 0.05). The difference in the profile of the serum myoglobin could therefore reflect restoration of arterial flow in myocardial cells which had not suffered the same period of ischemia. ST segment elevation may increase, decrease of remain stable at 120 minutes in patients revascularised and those remaining occluded. In 9 patients, the ST elevation increased compared with the initial electrocardiogram .(ABSTRACT TRUNCATED AT 250 WORDS)