Thrombolytic therapy in patients with acute coronary syndrome is not so widely used compared to coronary intervention, such as PTCA or stenting in Japan. This is probably because of the facts that the narrowing of the coronary artery is not completely restored after the thrombolytic therapy and that the coronary intervention is frequently necessary inspite of the administration of the thrombolytic agent. However, the thrombolytic therapy can be easily done in the peracute stage of myocardial infarction, and improvement of the prognosis of the affected patient may be possible. In this paper, the concepts as well as the effect of thrombolytic therapy and the characteristics of newly developed thrombolytic drugs are discussed.