AbstractThis thesis examines and discusses a sample of the medieval hypocausts (stone-heating ovens) in the Baltic area. The medieval construction is thoroughly explained as well as the antique hypocaust in order to establish a base for the following discussion. The medieval hypocaust has been almost forgotten for a long period of time. The last time someone dealt with this category of finds were in the 1960?s by Swedish archaeologist Iwar Andersson and in the 1970?s by Danish archaeologist Johannes Hertz.