Coronary vasospasms are usually indicated by ST elevation or depression in the electrocardiogram (ECG). To test the hypothesis that ST elevation represents more severe myocardial ischemia than does ST depression, we determined the coronary sinus blood flow (CSBF) and the transcardiac lactate extraction ratio (LER) in 19 selected patients who had focal vasospasms in the left anterior descending artery. In 10 patients, ergonovine (0.11 ± 0.02 mg, mean ± SEM) provoked severe (total or subtotal) coronary vasospasm with ST elevation. Under these conditions, CSBF significantly decreased (from 97 ± 8 ml/min to 79 ± 5 ml/min, p < 0.01) with a marked reduction in LER (from 29 ± 5% to -14 ± 6%, p < 0.01). In contrast, 10 vasospastic events with ST depression after ergonovine (0.15 ± 0.04 mg, NS) were recognized as mild spastic narrowing or severe spasms with well developed collateral circulation. Alteration of CSBF was significant in only a few patients and the overall CSBF response was non-significant (from 106 ± 12 ml/min to 103 ± 13 ml/min). The reduction in LER in this group was less pronounced than those in patients with ST elevation (p < 0.05). These results indicate that coronary vasospasm with ST elevation may be related to the more pronounced reduction in coronary blood flow accompanied by more severe myocardial ischemia. Such observations may support the contention that some ischemic events associated with ST elevation or depression can be interpreted as a continuous spectrum of vasospastic disorders.