The effect of quenching on the magnetic properties of polycrystalline Pr 0 . 5 Sr 0 . 5 MnO 3 has been investigated. Quenching samples from 1400 o C to room temperature in water (sample I) or in air (sample II) allows them to crystallize in two different systems and to exhibit different magnetic behavior at low temperature. Powder X-ray diffraction patterns for samples I and II could be indexed, respectively, in the rhombohedral perovskite structure with R3c space group and an orthorhombic one with Imma space group. Magnetization measurements show that both samples exhibit a paramagnetic-ferromagnetic transition at 280 K (sample I) and 265 K (sample II). At low temperature, sample I presents a ferromagnetic canted spin state or a mixture of ferromagnetic and canted phases, while sample II behaves as an antiferromagnet below 160 K.