Désiré Collen, born on 21 June 1943 in the Flemish town of Sint-Truiden as the first of two children of Frans Collen and Maria Hoebrechs, started his studies in medicine at the University of Leuven (KU Leuven) in 1961. Since his third year of the seven-year curriculum he combined his studies with research: first in the laboratory of Belgian physiologist Professor Joseph P. Bouckaert, and from the next year on in the Laboratory for Blood Coagulation under the direction of Professor Marc Verstraete. Under the guidance of young gastroenterologist Guido Tytgat and biochemist René De Vreker he studied the rate at which the coagulation proteins fibrinogen and plasminogen are cleared from the circulation. This early experience with biochemical lab work inspired Désiré Collen to become a researcher rather than a practicing general physician or medical specialist. Realising his knowledge in chemistry was inadequate, he combined his education in medicine with academic studies in chemistry. He graduated from the KU Leuven as Doctor in Medicine in 1968 and as Master ("Licentiaat") in Chemistry in 1969.