Background and Objective Previous study showed tenecteplase and alteplaxe were equovalent for 30-day mortality in the treatment of acute myocardial infarction. The purpose of this open-label, randomized, multi-center, angiographic trial was to assess the efficacy and safety of tenecteplase compared with alteplase in Chinese patients with acute myocardial infarction. Methods We recruited patients with acute ST-elevation myocardial infarction presenting within 6 hours of symptom onset from October, 2002 to March, 2004, in 5 hospitals in Beijing. After giving informed consent, patients were randomly assigned a single-bolus injection of tenecteplase (30-50 mg according to body weight) or front loaded alteplase (100 mg), and underwent coronary angiography at 90 min after starting the study drug. All patients received aspirin and heparin (target activated partial thromboplastin time 50-70 s). The primary efficacy end point was the rate of TIMI grade 3 flow at 90 minutes. Other efficacy end points included TIMI grade 2/3 flow at 90 minutes. Safety end points included all stroke, intracranial hemorrhage (ICH), moderate/severe hemorrhage (except for ICH), all-cause mortality at 30-days, and major non-fatal cardiac events at 30 days. Results Overall 110 patients were eligible for statistical analysis, with 58 patients assigned to receive tenecteplase and 52 patients to alteplase. Tenecteplase produced a rate of TIMI grade 3 flow at 90 minutes after the start of thrombolysis (68.4%) similar to that of alteplase (66.7%, P=1.0); the rates of TIMI grade 2 or 3 were similar for patients treated with tenecteplase versus alteplase (89.5% versus 80.4%, respectively, P=0.278). At 30 days, rates for all strokes were similar for the two groups (5.17% for tenecteplase and 1.92% for alteplase, P=0.62); rates of ICH were 3.45% and 1.92% (tenecteplase and rt-PA, P=1.00) respectively. The rate of moderate/severe hemorrhage was 8.62% with tenecteplase and 5.77% with alteplase (P=0.72); total mortality was almost identical in the two groups (13.8% versus 9.6%, respectively, P=0.565) while the rates of non-fatal cardiac complications were 10.35% and 11.54% (tenecteplase and alteplase￡?P=1.0). Conclusions The efficacy of a single-bolus, weightadjusted tenecteplase fibrinolytic regimen is equivalent to front-loaded alteplase in terms of the rates of TIMI grade 3 flow, and TIMI 2 or 3 flow, but the 30-day mortality and ICH in both groups was so high that the use of tenecteplase is not permitted in China. These negative safety results might be due to the high rate of percutaneous coronary intervention (PCI) and high dose of bolus heparin and suboptimal concomitant medical therapy during hospitalization, so further studies are needed to confirm the safety for tenecteplase in Chinese patients.