Current interest in spin electronics has generated a demand for materials in which magnetic properties occur side-by-side with a strong spin-dependent response of charge carriers. In this connection III-Mn-V ferromagnetic semiconductors –and GaMnAs in particular – continue to attract attention. One should emphasize that the success of any device based on spin polarization will depend not only on achieving an above-room-temperature Curie temperature Tc, but in equal measure on the presence of a strong interaction between magnetic moments and electronic bonds. It is therefore crucial to have a good understanding of the effect of magnetism occurring in the III-Mn-V system on its band properties. The most direct information on this process is usually obtained via magneto-optical experiments. In this talk I will present magnetic circular dichroism (MCD) results obtained on Ga1-xMnxAs films and explain their complex behavior in terms of a difference in the density of spin-up and spin-down states in the valence band brought about by the prescence of the Mn impurity band. The proposed solution is drastically different from that used successfully in II-Mn-VI diluted magnetic semiconductors (DMSs) based on the giant Zeeman shift resulting from the exchange mechanism between Mn moments and band carriers.