In an experiment conducted with the 130-kilowatt NASA Mod-0 wind turbine, vortex generators were installed on the low- pressure surfaces of the outboard 30% of the turbine blades. The subsequent improvement in airfoil section performance resulted in marked increases in power output. Between tip speed ratios of approximately 3.0 and 6.5, power coefficients were increased by 11.4 to 30.61. When these results were compared to data obtained in a vortex generator experiment performed with a Boeing Mod-2 wind turbine, similar trends were seen. Finally, using 3-dimensional wind tunnel data obtained from a full-scale test of a Mod-0 blade section in the NASA-Langley 30x60-foot wind tunnel, the wind turbine performance prediction code WINDlS was used to predict the effect of vortex generators on a Mod-0 wind turbine having blades similar (but not identical) to those with which the Mod-0 was operated during the rotating tests. Qualitative differences are ascribed to actual differences between the wind tunnel model and the operating turbine blades, and to the possible presence of spanwise flow on- the blades at moderate tip speed ratios.