The ever increasing strain on traditional centralized power generation and distribution systems has led to an increase in the use of distributed generation (DG) technologies. DG technologies are commonly found in urban areas that are sensitive to criteria pollutants, and as a result, they are subject to increasingly stringent emission regulations. Paralleling the growth of installed DG is the ever-increasing interest in hydrogen as an alternative fuel to natural gas. As a hydrogen infrastructure is developed, a desire to use this new fuel for DG applications will evolve. Microturbine generators (MTGs) are one example of DG technology that has emerged in this paradigm and are the technology of interest in the present work. To evaluate the potential role for hydrogen fired MTGs in this paradigm, understanding of what emission levels can be expected from such a system is needed The current study retrofits a natural gas fired MTG for operation on hydrogen and characterizes the resulting operability and emissions performance. The results of implementing design changes to improve emissions performance while maintaining stability and safety of the MTG when operating on hydrogen fuel are presented. The results also show improved stability limits which are utilized to help attain lower emissions of NOx. Further optimization is needed to achieve the NOx levels necessary to meet current regulations.Copyright © 2006 by ASME