The chemical phase content, crystal structure, and magnetization for the doped anion-deficient La1-xSrxMnO3-x/2 (x = 0, 0.05, 0.10, 0.20, 0.30) manganites have been studied. The samples undergo the structural phase transition from the O'-orthorhombic to the rhombohedric unit cell at x > 0.10. As doping level and oxygen deficiency increase the samples show a number of magnetic transitions. In the region of 0.05 ≤ x ≤ 0.20 the samples are inhomogeneous ferromagnets while at x = 0.30 they are cluster spin glasses. The temperature of the magnetic moment freezing is ∼45 K. The concentration dependences of the spontaneous magnetization and coercivity as well as magnetic phase diagram have been constructed. The magnetic properties of the anion-deficient Sr-doped samples may be interpreted on the basis of competition of the positive Mn3+(6)-O-Mn3+(6) and negative Mn3+(5)-O-Mn3+(6) isotropic superexchange interactions and impurity phase separation models. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.