A microscopic theory is used to analyze optical gain in InGaN/GaN quantum wells (QW). Experimental data are obtained from Hakki-Paoli measurements on edge-emitting lasers for different carrier densities. The simulations are based on the solution of the quantum kinetic Maxwell-Bloch equations, including many-body effects and a self-consistent treatment of piezoelectric fields. The results confirm the validity of a QW gain description for this material system with a substantial inhomogeneous broadening due to structural variation. They also give an estimate of the nonradiative recombination rate. (c) 2006 American Institute of Physics.