The orthorhombic perovskite, (La1-x/2Bix/2)(Fe 0.5Cr0.5)O3 was investigated for 0≤x≤1. Itsspace group, Pnma, compatible with the disordering of iron and chromium in the B sites, confirms previous observations. More importantly this compound is found to be an uncompensated weak ferromagnet, with a very peculiar zero magnetization behaviour, generally observed for ordered magnetic cations in the B sites. It exhibits a magnetic transition at high temperature (TC) above 450K, while the zero magnetization occurs between 100 and 160K depending on the x-value. The AC magnetic susceptibility study shows that this compound does not exhibit a spin glass or cluster glass behaviour, in contrast to what was suggested for the x = 0 compound. This zero magnetization phenomenon can be interpreted by the fact that this perovskite is an uncompensated weak ferromagnet, which consists of canted weak ferromagnetic domains and clusters of pure chromium and pure iron composition, antiferromagnetically coupled through Cr-O-Fe interactions. © 2009 IOP Publishing Ltd.