The origin of the Teutonic Order of Hospitalers St. Mary (Ordo Hospitalis S. Mariae Teutonicorum Hierosolymitani) is presented. The St. Mary Hospitaler Teutonic Order arrived in the XIIIth century to Pomezania, then inhabited by pagan Prussian tribes. The Knights of the Order started to Christianize the Prussians, then to conquer not only their territories but also those of neighboring Pomerania and others belonging to the Christian Kingdom of Poland. Selected events and dates are presented from the history of the independent state of Teutonic Order that existed on these territories for almost 300 years. The information presented is about the hospitals existing during this period of time; about the infirmaries located within the fortified castles build by the Order, and about other sanitary arrangements and problems. The names of medically qualified members of the Order and physicians employed by the Order who were not members, are also mentioned. A probable nephrological case (urolithiasis) in a High - Master of the Order is reported. Finally, information is presented about the guild of barber - surgeons functioning in the town of Gdansk, independently of the Teutonic Order.