Excitonic processes involving LA, TA, and LO phonons are studied in quantum wells. We have derived expressions for exciton–acoustic phonon interactions for both deformation potential and piezoelectric couplings. We have taken into account the effect of anisotropy of the valence band which gives rise to exciton–phonon interaction due to deformation potential coupling for both LA and TA phonons. The rates of excitonic relaxation are also derived involving all three types of phonons. Finally, the rates of phonon emissions are calculated in GaAs quantum wells.