This paper deals with the last mission of St Bruno of Querfurt (d.9 March 1009) which has received controversial treatment from a number of scholars working independently of each other. This state of affairs may be explained not only by reference to different preferences of scholarly research in the countries of east-central Europe, but also to the fact that the very sources of the martyrdom are rather problematic in themselves. Our research has shown that accounts produced by Peter Damian or Ademar of Chabannes must be taken more seriously than was the case up to now, since they provide details that, taken together with other sources, show that the martyrdom in question caused a mutual rivalry between Polish and Rus'ian rulers, Boleslaw and Vladimir, for the benefits that might have been derived from St Bruno's glorious death and possession of his relics. It is also to be emphasised that St Bruno's last mission was most promising to the local ruler named Nethimer who received baptism but finally failed to secure the gains of his new status as a Christian ruler. This tug of war between Polish and Rus' rulers may, at least in part, account for the fact that after some initial steps the incipient cult of St Bruno became extinct in their respective countries and his memory was condemned to the long centuries of virtual oblivion.