Theodoricus Ulsenius (Dirk van Ulsen, c. 1460-1508). Physician and humanist from the Northern Netherlands In the Renaissance period the interest of many intellectuals for the legacy of the Greeks and the Romans was overwhelming. We also find this attitude among medical doctors who devoted their attention more and more exclusively to Hippocrates and Galen. One of those humanistic doctors was the Dutch physician Theodericus Ulsenius (Dirk van Ulsen, c. 1460-1508). This article deals with three aspects of Ulsenius's activities in the medical field. In 1496 he published a poem on the newly broken out disease of syfilis, which was entitled Vaticinium in epidemicam scabiem. These hexameters with their allusions to antique literary, astrological and medical knowledge, is a typical product for a medical doctor who moved around in learned humanistic and artistic circles. Moreover Ulsenius held his own profession in very high esteem. Because of that he strongly propagated the use of the Roman title of Archiatrus for the official town physician. On these high ethical and social ideas on the medical profession, he expounded in an oration which he prepared at the occasion of his own appointment as a town physician of Nuremberg. This Protrepticus is also discussed. Lastly Ulsenius's edition of the Aphorisms of Hippocrates is treated. This incunable is especially interesting since the editor replaced Galens commentary by a didactic poem of his own. This Clinicus Pharmacandi Modus deals mainly with the use and misuse of pharmaceuticals in medical treatment.