Franciscus de Rivulo, the first composer from Gdansk to achieve European renown, cantor of the Marian church in that city, still remains a mysterious personage. Only last four years of his life (1560-64) are documented. The authoress argues that research of manuscripts containing his compositions can bring additional information and brings forward the results of this approach. Discussion of different spellings of the composer's name leads to a conclusion that the Latinized name Franciscus is the most appropriate form, because it appears as such in manuscripts and prints. His origins are investigated and new research results and hypotheses concerning his biography and compositions are presented