Sixteen panels of the ensemble of some 100 panels in the chapel of the Holy Cross in Marlstejn Castle (Bohemia), dating from 1357-65, have been studied in the laboratory. A number of unusual features have been established. The preparation of the beech-wood panels consists of two layers, a grey silicious one and a pure chalk layer. The painted forms often deviated from the black underdrawing executed by wide brush strokes. The incised outline is of secondary importance. In addition to the standard gilding on bolus there is also oil gilding applied to the profuse plastic ornaments that distinguish Theodoric's work. A film of oil-bound white lead with protein admixture serves to reduce the absorption of the medium and to reflect light. The preparation was completed by an oily isolation film for the painting identified as oil tempera with proteins. The complexion coloring and its modeling was executed alla prima without a dark underpainting. Coloristic richness of the garments was achieved by semi-translucent layers of colors radically differing from the basic layer. Patterns on the garments were executed with stencil. The technical procedure of Theodoric's murals in the chapel coincides closely with that of the painted panels. The methodology used for the analysis of a wide range of pigments and media is described. -- AATA