The radiative decay of free excitons with the emission of 0
1 or 2LO phonons has been observed in electroluminescence in CdS diodes operated in forward bias at temperatures in the range 40-77K. The line shapes and temperature dependence of the 1LO and 2LO phonon assisted replicas are discussed in terms of the distribution of kinetic energy of the excitons with an effective temperature equal to that of the lattice.