This paper attempts to describe the unique stresses imposed on MHD generator materials. This is done by reviewing experimental test histories of two generator designs represent-ing extremes in operating conditions and materials selection. Related experimental work, bearing on the importance of coal-ash slag properties to design functions, is also re-viewed. This latter is particularly critical to U.S. MHD development goals. The range of engineering conditions and materials attending the tests described in this review sug-gests a breadth of design choice which is probably less real than apparent. Engineering development, currently in progress and planned, is directed towards quantitative deter-mination of specific design and material influences on generator performance and dura-bility. Material requirements are closely interrelated with thermal, electrical, and ge-ometric design conditions, as this review will show. Finally, MHD test experience sum-marized here affirms the necessity for close engineering design and test discipline in the development of materials for power machinery applications.