The paper deals with the recent discovery of three previously unknown editions of the Krakow Catechism of the Reformed Church of the Polish-Lithuanian Commonwealth, which allows the author to correct the previous views on the historical evolution of the aforementioned catechism and helps him to properly reconstruct the chronology of the earliest editions (still considered lost). Moreover, newly discovered books offer a new insight into the editorial activity of the Polish printer Maciej Wirzbieta and his professional connections to the Lesser Poland community of the Reformed Church. As far as the history of the Reformed Protestantism is concerned, the discovery in question sheds new light on the contacts between the Lituanian and the Lesser Poland communities of the Reformed Church in the second half of the 16 th century and shows a continuity of catechesis (based on the Krakow Catechism ) from the end of 16 th to the end of 18 th century.