Progressive multiple sclerosis (MS) consists of 3 phenotypic subtypes: secondary progressive MS, primary progressive MS, and progressive relapsing MS. There has been a paucity of approved treatments for these subtypes possibly driven by irreversible neurodegeneration within the central nervous system and not amenable to drugs that target inflammation. This article reviews magnetic resonance imaging and clinical data that show that progression may occur early in the course of MS and specific subsets of progressive patients may respond to disease modifying drugs.