In 1486 Drohobych returned to Krakow. He started his medical practice and also taught medicine at Krakow University. Similar to his peers from Bologna, he based his lectures on the works of Hippocrates, Galen, and Avicenna. A few years later, he received his professorship in medicine and became the doctor of the Polish king Casimir IV Jagiellon. In 1492 he became the Dean of the Department of Medicine. It was customary at that time for professors to have off-site meetings to discuss with students issues that did not fit the official scientific doctrine. Copernicus attended Drohobych's meetings, however it is not certain whether the former had an influence on the latter.