Global and regional left ventricular performances were evaluated with equilibrium radionuclide angiocardiography in patients in the Thrombolysis in Myocardial Infarction (TIMI) II trial at the time of hospital discharge. Studies at rest were available in 1,162 (69%) of the invasive and 1,150 (69%) of the conservative strategy patients, and exercise studies in 1,133 (67%) of the invasive and 1,145 (69%) of the conservative patients. Repeat studies were performed at the time of 6-week follow-up. Global and regional ejection fraction at rest were both comparable in patients assigned to each of the treatment strategies. However, at the time of hospital discharge patients in the invasive strategy had normal exercise responses more frequently (29.7 vs 25.8% p = 0.01), greater peak exercise LV ejection fraction (54.8 +/- 13.8% vs 53.1 +/- 14.1%, p = 0.004), greater exercise--rest change in LV ejection fraction (3.7 +/- 6.7% vs 2.7 +/- 7.2%, p less than 0.001) and greater peak exercise infarct zone regional ejection fraction (53.2 +/- 31.1% vs 50.3 +/- 33.0%, p less than 0.001) than patients assigned to the conservative strategy. At 6-week follow-up these differences between treatment strategies were no longer evident. When data were restricted to those collected at comparable work loads, similar differences in hospital discharge exercise performance between invasive vs conservative strategy patients were observed. Thus, there is a small transient difference in exercise global and regional LV performance associated with an invasive as opposed to conservative strategy after thrombolytic therapy. These differences are noted at the time of hospital discharge but not at 6 weeks, and are unlikely to confer clinical benefit.