The optical response of hot carriers in III-V compounds is modeled within a density matrix formalism. As a starting point for the calculation of the luminescence, a four-point electron-hole density matrix has to be used. the band structure is described by a realistic model including all hole subbands and Γ-, L, and X-valleys of the conduction band. the theory is compared in detail with recent time-resolved and spectrally resolved luminescence up-conversion results. Satisfactory agreement can be obtained even with a rather simple exponential relaxation ansatz for the energies of internally thermalized electron and hole distributions. Arguments are given that the detected luminescence intensity must be distinguished from the photon generation rate. © 1992 IEEE.