Demyelination is a pathological hallmark of multiple sclerosis (MS), a chronic autoimmune disorder of the central nervous system (CNS) that affects mainly young people in western countries. Recent studies have shown that remyelination can be accomplished by supplying demyelinated regions with myelinogenic cells or neural stem cells via transplantation. The remyelinating effect of these cells may be via one or more mechanisms, including: 1) as an immunomodulator by producing soluble factors; 2) direct cell replacement by differentiating into neural and glial cells in the lesion; and 3) indirect action by promoting neural and glial differentiation of endogenous cells. Identifying these mechanisms will help in choosing an optimal and more effective approach for cell-based therapy. Here we present a brief view focusing on myelin-forming cell types that can be used for cell transplantation and draw on a variety of recent experimental findings to speculate on the likely future evolution of remyelinating therapies.