The treatise on the Eucharist is the last completed part of St Thomas Aquinas´ Summa Theologiae (STh III, q. 73-83). The following writing on the sacrament of penance has remained an unfinished torso. This book presents a Czech translation of the treatise accompanied by a critical apparatus as well as explanatory notes. The translation itself is preceded by an extensive introductory study and a glossary covering key terms.