A stereological analysis of electron backscatter diffraction data has been used to measure the five-parameter grain boundary character distribution of chemically modified 316LN stainless steel exposed to both elevated and cryogenic temperature. The results were analyzed to determine if the thermal treatments induced any significant changes in the overall grain boundary character distribution and fractional twin density. The results of this study show that the grain boundary character distribution of this steel is very similar to other FCC polycrystals and not affected by typical thermal treatments used in processing or the cryogenic temperatures employed during service.