In this paper we summarize recent developments in the experimental study of the intrinsic gain and recombination characteristics of GaInP quantum wells. Derivation of gain spectra from spontaneous emission spectra observed through a top-contact window is limited to radiation of TE polarization an dit is necessary to assume the carrier system is in quasi equilibrium to calibrate the data into real units. These difficulties are overcome by deriving the gain and spontaneous emission spectra from the amplified spontaneous emission spectra observed from the end of the structure as a function of the pumped stripe length. The emission spectra can be calibrated by identifying the region where the carrier distributions are fully inverted, without assuming that quasi-equilibrium conditions are established. We have determined the modal gain and spontaneous emission spectra for both TE and TM polarization for a tensile strained GaInP quantum well structure, and have obtained the TM and TEy gains as functions of the total experimentally-determined radiative recombination current.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.