The article analyses Epistolae Generalium ad Nostros, Jesuit correspondence within the Order extant in the Archivum Romanum Societatis Iesu representing a general's letters to superiors of individual provinces and the common members of the Society. On an example of a Jesuit historian Maximilianus Weitrowsky, it shows what bio-bibliographic information can be obtained for compiling a biography of a particular Jesuit.