We have investigated the optical transitions in individual self-assembled InAs/Al0.6Ga0.4As quantum dots (QDs) by means of scanning-tunneling-microscope (STM) light-emission spectroscopy. Localized bright features were observed in the spectrally resolved light intensity images measured by injecting electrons from the STM tip. The light emission spectra measured over the bright features showed single emission peaks having different peak energies with linewidths of 30–45 meV. By comparing these results with atomic-force-microscope images and photoluminescence (PL) spectra, we have identified the bright features with the ground-state interband transition from individual InAs QDs. The emission peak energies were compared with the transition energies calculated for pyramidal-shaped QD structures, based on a single-band and constant-confining-potential model. A reasonable agreement was obtained between the experimental and calculated results. The emission linewidth of individual dots is much narrower than the linewidth (∼200 meV) measured by PL from an ensemble of dots. This fact demonstrates the importance of measuring the linewidth for individual dots rather than for an ensemble of dots with size distribution. © 2004 American Institute of Physics.