We have investigated the crystal structure and magnetic properties for polycrystalline samples of LaMn1-xFexO3+y, in the whole range 0.0x1.0, prepared by solid state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn-Teller distortion, thus favoring a ferromagnetic (FM) superexchange interaction between Mn3+-O-Mn3+. For x=0.0 the oxygen excess (y≈0.09) produces vacancies in the La and Mn sites and generates a fraction around 18% of Mn4+ ions and 82% of the usual Mn3+ ions, with possible double-exchange interaction between them. The Fe doping in this system is known to produce only stable Fe3+ ions. We find an evolution from a fairly strong FM phase with a Curie temperature TC ∼160 K, for x=0.0, to an antiferromagnetic (AFM) phase with TN =790 K, for x=1.0, accompanied by clear signatures of a cluster-glass behavior. For intermediate Fe contents a mixed-phase state occurs, with a gradual decrease (increase) in the FM (AFM) phase, accompanied by a systematic transition broadening for 0.2<x<0.7. A model based on the expected exchange interaction among the various magnetic-ion types accounts very well for the saturation magnetization (MS) dependence on Fe doping. © 2009 American Institute of Physics.