The structures, ferromagnetism, spin glass and spin states of Co and Mn in a polycrystalline ceramic samples of GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x = 0.2, 0.3, 0.4, 0.5) are presented. X-ray diffraction show that all the samples are single phase and crystallize as orthorhombic structures and that the lattice parameters gradually increase with x. Spin glass state and two peak features (corresponding to first order ferromagnetic and second order transition) in dc and ac susceptibility are observed. Curie-Wise fitting on the inverse susceptibility-temperature plots indicates that the valences of Co or Mn changed from 2+ or 4+ to 3+ when Co amount increases. Possible spin state transformation of Co and Mn is also suggested.