This paper describes histochemical data on 2 oxidative enzymes (succinic dehydrogenase, DPN-diaphorase), 2 hydrolytic enzymes (acid and alkaline phosphatase), and data on mitochondria as to their relationship to the histopathology of multiple sclerosis. It represents an application to neuropathology of extensive histochemical mappings of enzyme activity in the normal brain.8,10-13 Such studies provided an abundance of data on gradations and on patterns of oxidative enzymatic activity in nuclei of the brain, as documented recently in a histochemical atlas of the cat brain stem.12 An effort is being made at present to provide a complete and detailed histochemical mapping of the human brain. A study of DPN-diaphorase activity in human white matter showed an inverse relationship of the enzyme activity in axons and in glia cells.13 Certain tracts contained most of their enzyme activity in glial perikarya and very little in axons; these tracts also showed high total