In order to study the stereochemistry of equatorial photosubstitution in Cr(III) complexes, [trans-Cr(2,3,2-tet)-(CN)2]ClO4(2,3,2-tet = 1,9-diamino-3,7-diazanonane) has been synthesized and characterized. Its photoaquation has been studied by proton uptake and cyanide release measurements. The molecule photoaquates one end of the 2,3,2-tet ligand with a quantum yield of 0.09 +/- 0.01, while any photochemical cyanide loss has a quantum yield of less-than-or-equal-to 0.02. That the photoproduct has the cyanide ligands in the trans configuration is strongly indicated by its thermal recoordination at pH 6 to the starting complex, as well as by the UV-vis spectrum of the photoproduct. These results show that photosubstitution of the equatorial ligand in this complex is stereoretentive, in contrast to the stereochemical change that accompanies loss of the equatorial ligand in other Cr(III) complexes. Nanosecond laser flash photolysis experiments with conductivity detection showed that 100% of the reaction occurs as a single-exponential growth with a lifetime of 26 +/- 1 mus, in good agreement with the observed doublet state emission lifetime at 21-degrees-C of 28 +/- 1 mus. The results are discussed in the context of data on analogous cyano complexes, the angular overlap theory of chromium(III) photochemistry including the Jahn-Teller distortions of the intermediates, and the behavior of photoinert cyclam complexes.