Piacenza, Bibl. Capitolare cod. 63 contains the medieval collection of texts, selected, modified and divided in 48 lectiones to serve as the prosaic part of the divine office to celebrate Justina, Piacenza's patron saint, and Cyprian of Antioch during the octave from their heavenly birth-day on September 26 to the Octave on October 3. The readings present two versions of the legend of Justina and Cyprian who suffered martyrdom in Nicomedia during the persecutions of the Roman emperor Diocletian in 304. According to the legend Justina converted to the Christian faith. As she went to church one day, a grammarian named Agladius caught sight of her and wanted to marry her. When he failed to obtain her consent, he turned to Cyprian, the major magician in Antioch, who called the devil and his demons to help Agladius. When they failed to conquer the Christian virgin, even Cyprian converted to the Christian faith and served as priest and bishop till he and Justina were decapitated. The corpses were brought to Rome, and their relics found their resting place in Piacenza in 1001. In addition to the two legends parts of a Greek opus entitled Confessions and penetance, attributed to Cyprian, had been translated into Latin to serve as readings for two of the days in the octave. The edition is part of a planned project in the Ars edendi programme, i.e. a modified diplomatic edition of the medieval Lectionarium Placentinum from the cathedral of Piacenza in the second half of the twelfth century. In order to offer scholars who are not specialized in Latin a possibility to study and interpret the various parts of these lectiones, an English translation is included as well as an introduction to the medieval cult and veneration of Justina in Piacenza, a description of the liturgical frame and the contents of the readings and the editorial principles. Hopefully this edition might provide scholars with an instrument for studies in other fields of medieval research such as Latin language and literature, biblical exegesis, liturgy, theology, hagiography, history of ideas, as well as Latin translations of Greek texts.