Jean Luc D'Hautcourt passed away suddenly on October 12, 2005, shortly after the 10th Annual Congress of the Association Française de Cytométrie (AFC). Shortly before this jubilee, we learnt that he was incurably ill. At the jubilee, the AFC membership paid tribute to him and wished him well. His untimely death came as a shock to us all. As a technical engineer, Jean Luc was on the spot when the first cytometer in his home country, Belgium, was installed in the late 70s. Later, Jean Luc moved to the clinical laboratory setting where he put clinical cytometry into practice. Jean Luc was a keen member of the Flow Cytometry Association (FCA) at that time; he organized the 1991 FCA Congress in Mons and became member of the AFC at the time of its inception in 1993. During the four years as Chairman of AFC, Jean Luc never failed to give this association his unstinting support and wisdom. He chaired AFC's annual congresses in Rouen, Marseille, Toulouse, and Dijon, each of which has been highly successful. During this time, he succeeded and devoted much time in establishing AFC's “journées thématiques” (thematic days). Jean Luc contributed significantly to AFC's national reputation, as a result of which AFC became the only and indispensable discussion partner for clinical cytometry in France. As a result of Jean Luc's efforts in developing AFC's international relations, the role of the society on the international stage became prominent, which culminated in the excellent 2000 international congress of the International Society for Analytical Cytology (ISAC) that was hosted by AFC in Montpelier, France. Importantly, Jean Luc was very much responsible for establishing and promoting close ties with the Belgian Association for Analytical Cytometry (ABCA/BVAC), since its inception in 1996. Scientifically, Jean Luc was not only a member of several working groups and societies, such as the French Groupe d'Etude Immunologique des Leucémies (GEIL) and ISAC, but also was a cofounder of the European Working Group on Clinical Cell Analysis (EWGCCA, later European Society for Clinical Cell Analysis [ESCCA]), of which he served as secretary from 2001 to 2004. Jean Luc was a fervent promoter of quality assurance within the field of clinical cytometry, as reviewed by Brando et al. in this issue (1) and commemorated during his keynote lecture at the 6th Euroconference on Clinical Cell Analysis, organized in Stresa (Italy) by ESCCA from September 14–16, 2006. Jean Luc's contributions to this field have been highlighted during AFC's Journée Thématique, held to his honour on February 2, 1996, as outlined by Bayer and colleagues in this issue (2). Jean Luc was also involved in teaching cytometry; not only within the institutional framework, but also further afield. Specifically, he contributed to EWGCCA's annual educational workshops at the University of Urbino (Italy) between 1997 and 2002. To this end, many have gained much insight from his advice and expertise. The above all testify to the selfless and enormous contributions Jean Luc has made and given to our common field of interest. Jean Luc was a warm person, a man who enjoyed life to its full. He had a tremendous sense of humor, and was always in for a good joke. His death leaves a huge gap in our world. It is, in particular, a tragedy for the many members of his family, especially the youngest of his 13 children. We convey our deepest sympathy to them all on their sad loss. In this issue of Clinical Cytometry, we pay tribute to Jean Luc: not only to thank him for all he has done and meant to us, but also as a token of our everlasting friendship.