The crystal structure and some magnetic properties were investigated for polycrystalline samples of LaMn1-x Fex O3+y, prepared by solid-state reaction in air. All samples show the ORT-2 orthorhombic structure that suppresses the Jahn-Teller distortion and favors a ferromagnetic (FM) superexchange interaction between Mn3+ -O- Mn3+. An evolution from a fairly strong FM phase, for x=0.0, to an antiferromagnetic (AFM) phase, for x=1.0, was observed. For intermediate Fe contents, a magnetic mixed-phase state occurs, with a gradual decrease (increase) in the FM (AFM) phase as x increases. A clear cluster-spin-glass (CG) behavior is observed in our samples for x0.1, where FM coupling dominates. In this case, the Vogel-Fulcher law describes very well the CG dynamics, giving reasonable values for the fitted parameters. © 2010 American Institute of Physics.