Treatment studies in multiple sclerosis and the experimental murine model of Theiler's virus encephalomyelitis have suggested that intravenous immunoglobulins (IVIg) promote central nervous system remyelination. It is not clear if this results from a direct effect on myelinating oligodendroglial cells, or from suppression of the immune response permitting better endogenous repair. We systematically explored the effects of IVIg on various aspects of oligodendrocyte precursor cell (OPC) behaviour in vitro. Neither proliferation, differentiation nor migration of OPC was affected by IVIg. These results argue against a direct effect of IVIg on remyelination and are in favour of an indirect yet not clearly defined mechanism that supports remyelination.