We report formation and optical properties of site-controlled, multi-stack InGaAs/GaAs quantum dots (QDs) embedded in GaAs nanowires (NWs) by selective metalorganic chemical vapor deposition. InGaAs/GaAs QDs are realized in GaAs NWs grown on patterned GaAs(111)B substrates in the form of InGaAs/GaAs heterostructures and identified by structural analyses and photoluminescence characterization. Optical characterization at 10 K corroborates formation of high-quality, multi-stack InGaAs/GaAs QD-in-NWs up to 50-stack without degradation of PL intensities. In addition, light emission at room temperature from multi-stack InGaAs/GaAs QDs embedded in GaAs NWs is realized. These results would enable the realization of high-performance IBSCs based on site-controlled QD-in-NWs utilizing existing, well-established NW growth technologies on a GaAs platform. (C) 2012 Elsevier B.V. All rights reserved.