The new perovskite (Bi0.5Sr0.5)(Co 0.5Ru0.5)O3 has been prepared under high pressure (10 GPa) and temperature (900 °C). The room-temperature crystal structure is described by the space group Pnma (a = 5.5702(3), b = 7.8793(5) and c = 5.5599(4) Å) with no observed order between Bi and Sr or between Co and Ru cations. This material shows antiferromagnetic spin ordering or freezing below 50 K and a paramagnetic moment of 4.07 μB per formula unit at high temperatures, consistent with the presence of high-spin Co2+ or Co3+ ions. (Bi0.5Sr0.5HCo 0.5Ru0.5)O3 is a variable range hopping semiconductor between 40 and 300 K with a small negative magnetoresistance. © 2008 Verlag der Zeitschrift für Naturforschung, Tübingen.