The compounds Cu 2 3 Ge 1 3 Cr 2S 4 have been shown to possess magnetic properties characteristic for spin glasses (SG). The critical behaviour of these compounds have been studied by means of the nonlinear susceptibility χ n1 in the region of freezing temperature T f that is defined as the temperature of maximum on the χ n1( T) curve. The critical exponents γ, δ and β have been determined. The temperature T f' of the maximum on the curves for the dependences of the initial susceptibility on T measured in an ac magnetic field has been found to depend on the frequency of measurements, according to the Vogel-Fulcher law, the constant T 0 being equal to T f. In these semiconductor compounds the giant negative isotropic magnetoresistance Δϱ / ϱ has been observed, that reaches 80% at H = 30 kOe. A maximum in T f has been observed on the dependence Δϱ / ϱ( T), which is similar to that Δϱ / ϱ( T) in the region of magnetic ordering temperature in magnetic semiconductors.