Large Cr:AlPO 4-5 single crystals have been characterized by microcrystal absorption spectros copy using a CCD array spectrometer and a fiber optics technique. For Cr 3+ in AlPO 4-5 crystals a polarization-dependent absorption is observed. This indicates an anisotropic coordination of Cr 3+ distorted by the molecular sieve structure. Polarized absorption measurements on Cr: AlPO 4-5 crystals loaded with p-nitrodimethyl aniline (pNDMA) and with p-nitroaniline (pNA) show a strong alignment of the guest molecules in the pore system parallel to the straight channels. The reduced ability to adsorb large molecules into the channels of the Cr:AlPO 4-5 crystals supports the hypothesis of the nonframework incorporation of Cr 3+.