Chromium doping of wide band-gap 111-V semiconductors is known to produce semiinsulating material by compensation of residual shallow donors. Despite the great technological importance of Cr-doped 111-V compounds as substrates for device fabrication the physical nature of the Cr centers controlling the electrical properties in certain materials is still subject of investigation. Thus, in contrast to what happens in GaAs and InP the behavior of Cr in gallium phosphide is very poorly understood I l l . The location of the chromium-related energy levels within band gap is extremely unclear 12, 31 and the theoretically predicted positions differ from the experimentally determined ones 141. Several methods like DLTS, photocapacitance, photo-ESR, photoluminescence (PL) , and photoconductivity (PC) (a detailed review is given in /I/) have been employed for the determination of the position of Cr centers in Gap. The aim of the present note is to investigate the position of the Cr levels in semi-insulating Gap. For this purpose we have used p-type samples with room temperature resistivity greater than 10 Qcm, that is the Fermi level lies about 0.8 to 1 eV above the valence band, and studied the material impurity photoconductivity. In addition, the diffusion photocurrent under continuous and chopped extrinsic (impurity) illumination has been investigated in order to determine the photoinduced transitions between the bands and the Cr levels. It must be mentioned that all measurements were performed at room temperature. It is well known that chromium introduces three levels in Gap, two acceptors and a donor one. In the case of semi-insulating material, where the Fermi level lies close to midgap, only the two acceptor levels are observed 131. Thus under extrinsic illumination valence band electrons can be excited into the Cr single and double acceptors and photoconductivity is carried mainly by excess holes. Therefore the impurity PC is expected to show two thresholds, one for each level.