The floor tiles are discusses with the objective of identifying the products and reconstructing their manufacturing process. The centers in question were important in the Middle Ages, objects of rivalry between the Ruthenian and Piast princes. The tiles from Przemysl originated specifically from either Przemysl - Castle or Zasanie (site 89), where the remains of a pottery manufacturing workshop were discovered. With the exception of one example excavated at the fort (site 2), the ceramic tiles from Drohiczyn came from a surface survey carried out before World War II. At Chelm the tiles were uncovered on site 144 and from 11-13 Lubelska Street. In Stolpie, the tiles were found in layers connected with the first two phases of a tower complex located there. The tiles in question are dated to the end of the 12th/beginning of the 13th c. through the middle of the 14th c. The tiles from Chelm and Stolpie were produced from ferruginous and kaolin clays. In most cases, tile thickness oscillated around 2.5 cm; moreover, some of the tiles from Stolpie were about 3.5 cm thick and had narrower edges. The overall shape was that of an elongated rectangle. The only two whole tiles came from Drohiczyn have a sharper angle of beveling and are all coated with brown glaze. The tiles were made most probably in moulds devoid of a bottom part. The mould was filled with a ceramic mass and the face leveled. The underside of the tiles often shows post-production traces, like a sand bed or tool marks which are witness to prying a given piece from a moulding table. Items from different centers differ in dimensions, angle of beveling of the sides and shape: the Przemysl tiles are relatively thin (about 2.1 cm), seldom exceeding 2.5 cm, and they are on the whole unglazed; tiles from Zasanie look like production waste; tiles found at Przemysl Castle are like those from the pottery workshop site. It should be noted, however, that the tiles from the Castle can be both triangular and probably rectangular in shape, while those from the settlement are solely rectangular. The analyses demonstrated most of the tiles to be coated with a non-alkaline lead glaze. The glaze of tiles from Chelm and Drohiczyn belong to the lead-lime-silica type. Among the Przemysl tiles, one example of an alkaline lead-potassium-lime-silica glaze was recorded. The use of a lead-potassium recipe is believed to be typical of Early Medieval Ruthenian glass-making. The Stolpie and Chelm tiles form the most homogeneous sets. Some of the tiles from Stolpie demonstrated a chemical composition of the glaze very similar to that of the tiles from Castle Hill in Przemysl. Even so, the tiles from Przemysl are chronologically later; hence there is no reason to seek any direct contacts or influence. The same is true of the tiles made in Chelm and Drohiczyn - they differ in morphology as much as in the chemical composition of the glaze. Drohiczyn has yielded none of the kaolin-clay tiles that predominate in Chelm and Stolpie. Indeed, Drohiczyn appears to have been a separate center producing glazed pottery as indicated by finds of glazed vessels. Dendrograms illustrating the similarities in glaze composition of the floor tiles and pottery vessels from Chelm and Stolpie, as well as from Przemysl indicate a similar glaze recipe applied in the production of both categories of objects. The tiles from the sites appear to have the nearest parallels among finds from present-day Belarus and Ukraine. Figs 6, tables 2.