We present the Hamburg/RASS Catalogue ( HRC ) of optical identifications of X-ray sources at high-galactic latitude .
The HRC includes all X-ray sources from the ROSAT Bright Source Catalogue ( RASS-BSC ) with galactic latitude |b| \geq 30 \degr and declination \delta \geq 0 \degr .
In this part of the sky covering \sim 10 000 deg ^ { 2 } the RASS-BSC contains 5341 X-ray sources .
For the optical identification we used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey ( HQS ) which are now available in digitized form .
The limiting magnitudes are 18.5 and 20 , respectively .
For 82 % of the selected RASS-BSC an identification could be given .
For the rest either no counterpart was visible in the error circle or a plausible identification was not possible .
With \sim 42 % AGN represent the largest group of X-ray emitters , \sim 31 % have a stellar counterpart , whereas galaxies and cluster of galaxies comprise only \sim 4 % and \sim 5 % , respectively .
In \sim 3 % of the RASS-BSC sources no object was visible on our blue direct plates within 40″ around the X-ray source position .
The catalogue is used as a source for the selection of ( nearly ) complete samples of the various classes of X-ray emitters .