Spatially, spectrally, and temporally resolved cathodoluminescence ͑CL͒ techniques have been employed to examine the optical properties and kinetics of carrier relaxation for metalorganic chemical vapor deposition grown InGaN/GaN single quantum wells ͑QWs͒. Cathodoluminescence wavelength imaging of the QW sample revealed local band gap variations, indicating the presence of local In composition fluctuations and segregation during growth. A detailed time-resolved CL study shows that carriers generated in the boundary regions will diffuse toward and recombine at InN-rich centers, resulting in a strong lateral excitonic localization prior to radiative recombination.