This review contains the results of EPR/ENDOR experiments on DNA constituents in the solid-state. Most of the results presented involve single crystals of the DNA bases, nucleosides and nucleotides. The emphasis is on low-temperature ENDOR results. Typical experiments involve irradiations at or near helium temperatures in attempts to determine the primary radiation induced oxidation and reduction products. The use of the ENDOR technique allows one to determine the protonation state of the initial products. Subsequent warming of the sample facilitates a study of the reactions that the primary products undergo. A summary of the results is provided to show the relevance the study of model compounds has in understanding the radiation chemistry of DNA.