We investigated the impact of primary angioplasty compared with thrombolysis in 894 patients with ST elevation acute myocardial infarction and electrocardiographic grades II and III ischemia on enrollment. Patients were divided into 2 groups based on the enrollment electrocardiogram - grade III: (1) absence of an S wave below the isoelectric baseline in leads that usually have a terminal S configuration (leads V1 to V3), or (2) ST J-point amplitude ≥50% of the R-wave amplitude in all other leads. To be included in the grade III group, grade III criteria in ≥2 adjacent leads were required. Patients with ST elevation but without grade III criteria were classified as having grade II. In-hospital mortality was 3.2% and 6.8% in the grade II (n = 616) and grade III (n = 278) groups, respectively (p = 0.016). In the grade II group, in-hospital mortality was similar in the thrombolysis and angioplasty subgroups (3.2% and 3.3%, p = 0.941). In patients with grade III, in-hospital mortality was 6.4% and 7.3%, respectively (p = 0.762). The odds ratio for the grade III group for death with thrombolysis was 2.06 (95% confidence intervals [CI] 0.82 to 5.19; p = 0.125); the odds ratio for primary angioplasty was 2.30 (95% CI 0.93 to 5.66; p = 0.07). In the thrombolysis group, reinfarction occurred in 3.3% and 6.5% of the grade II and grade III subgroups (p = 0.137). In the angioplasty group, reinfarction occurred in 1.3% and 4.4%, respectively (p = 0.239). Grade III ischemia on admission was associated with higher in-hospital and 30-day mortality and a higher rate of reinfarction. There was no difference in mortality between primary angioplasty and thrombolysis in the grade II and grade III ischemia patients.