The publication provides full documentation for the project "Repertorium of the Old Bulgarian Literature and Letters", a long-term initiative of the Department of Old Bulgarian Literature at the Institute of Literature (Bulgarian Aacademy of Sciences), which is based on XML technologies. The guidelines include an overview both of the principles and techniques of encoding with explanation of different options and solutions for the description of the Slavic manuscripts drawing on scholars experience. Numerous examples illustrate mark up used in the electronic description of the codicology, textology and language of the medieval manuscripts.