This book is made possible by the enthusiastic contributions of the authors of the chapters. They have been invited from young and active scientists in the field of t-PA research. I am grateful for their contribution and for the fact that all accepted the specifications of their chapter in order to obtain a structured book. Inevitably, some overlap does exist; on the one hand to enable controversial or unsettled areas to be discussed by the different experts with a different approach and background.It is a particular pleasure and honor that Dr. T. Astrup, as an eye-witness and essential contributor to the history of t-PA discovery and research, gives a unique account of the history of t-PA research in the first chapter of the book.