High-indium-content InGaN/GaN multiple-quantum-well structures grown by low-pressure metalorganic chemical-vapor deposition have been studied by photoluminescence and optical pumping at room temperature and 25 K. The results show that the annealing process reduces the compositional fluctuation of indium content owing to diffusion and can make the quantum-well structures more identical everywhere in the active region. Several stimulated-emission peaks were observed in the spectra of optical pumping in edge-emitting geometry. These peaks result from interband transitions between quantized levels in the quantum well. By solving the time-independent Schrödinger equation, the interband transitions in the quantum well corresponding to each stimulated-emission peak in optical-pumping spectra can be identified. The band offset parameter ΔΕC/ΔΕg = 0.38 was obtained.