Gut ist eine Lehrart, wo man vom Bekannten zum Unbekannten fortschreitet; schön ist sie, wenn sie sokratisch ist, d.i. wenn sie dieselben Wahrheiten aus dem Kopf und Herzen des Zuhörers herausfragt. Bei der ersten werden dem Verstand seine Uberzeugungen in Form abgefordert, bei der zweiten sie ihm abgelockt. Professor Friederich Schiller Jena, in a letter written on 23 February 1793 to his friend and supporter Körner, father of the poet Theodor Körner. Established clinicians and scientists as weil as students aga in tried the Wilsede experiment for three days and nights and learned from each other. In our fourth Wilsede meeting on "Modern Trends in Human Leukemia" we concentrated once again on questions re gar ding the practical application of research and its benefits to the patient. The main emphasis of leukemia research has changed since the first Wilsede meeting in 1973. Virology is no longer the sole interest. Advances in immunology and cell genetics and a better understanding of Dr. h. c. Alfred Toepfer speeking with participants of the meeting in Wilsede XXI Arrival and discussion of participants in front of the meeting pI ace "De Emmenhoff" XXII Personal and scientific discussion in Wilsede June 1980 Fotos: R. Völs XXIII the mechanisms regulating normal and pathological blood cell differen- tiation have had a considerable impact on the direction of leukemia research.