He was born in 1943 at Breskens, The Netherlands and studied Medicine at the University of Amsterdam. After graduation in 1970, he was educated to become an internist in St Joseph Hospital, Eindhoven, The Netherlands. In 1975 he moved to the Department of Hematology of the University Hospital at Nijmegen, where he completed his Ph.D. thesis on "Spontaneous lymphocyte transformation in Hodgkin's disease" and became Head of the Clinical Section of Hematology. His major interests are the treatment of malignant lymphomas and the supportive care for immunocompromised patients. From 1995 to 2001 he served as chairman of "Invasive Fungal Infections Cooperative Group" of the European Organisation for Research and Treatment of Cancer (EORTC). In 1997 he was appointed Professor of Medicine (van Vlissingen chair) and Head of the Department for Bloodtransfusion Service and Transplant Immunology of the University Medical Center at Nijmegen. He was and is a member of many advisory and editorial boards. He delivered numerous lectures all over the world; more than 200 articles in journals and books on the treatment of bacterial and fungal infections emphasize his contribution to the field.