The thermodynamic aspects of nonmetallic element (i.e., oxygen, nitrogen, and carbon) inter-actions have been analyzed for certain refractory metal-litkium systems of interest for controlled thermonuclear reactor applications. The results provide a basis for further experimental work necessary to establish the operating limitations of potential containment materials for lithium under controlled thermonuclear reactor conditions. The refractory metals niobium, vanadium, and molybdenum are considered as base metals for the containment of lithium; and titanium, zirconium, and chromium are of interest as potential alloying elements. Nonmetallic element interactions between refractory metals and lithium are analyzed in terms of the equilibrium distribution coefficients and the nonmetallic elements concentrations in lithium sufficient for compound (i.e., oxide, nitride, or carbide) formation to occur. The types of interactions, viz., embrittlement, compound formation, reduction in strength, or lithium penetration of the refractory metals, which will probably have the greatest effect on the corrosion rates and mechanical properties of niobium, vanadium, and molybdenum in a lithium environment are discussed. Additional compatibility effects produced by alloying these refractory metals with either zirconium, titanium, or chromium are discussed. The importance of a capability to monitor and control carbon and nitrogen at low concentrations in lithium is emphasized, as is the need to establish the levels at which these impurities can be maintained in a large lithium system.