The optical absorption and fluorescence spectra of two spinels, ZnAl2O4:Cr3+ and MgAl2O4:Cr3+ have been measured at various temperatures between 2°K and room temperature. The data have been fitted to a crystal-field theory which includes spin-orbit coupling and the trigonal field of the D3d site. The parameters for a best fit for both crystals were: Δ = 18 250 cm−1, B = 700 cm−1, C = 3200 cm−1, ζ = 250 cm−1, ν = −200 cm−1, ν′ = −1700 cm−1, and k = 0.7. The E2 splitting was directly observed optically for both spinels, and in the case of the ZnAl2O4:Cr3+, the A24 splitting was also observed. In addition to fitting the energies and zero-field splittings, the theory gave values of absolute R-line intensities and lifetimes which agree well with observed values. Vibrational sidebands and pair lines observed in fluorescence were identified.