The central nervous system response to injury and inflammation commonly includes astrocytosis. This process, which is manifest by astrocyte hypertrophy and proliferation, is particularly prominent in multiple sclerosis (MS), where in chronic lesions it may contribute to the lack of repair by restricting the migration of remyelinating cells. Interferon-beta (IFN-beta) modestly reduces the frequency of relapses in MS and may have a small effect on the accumulation of permanent disability. Here, we show that IFN-P inhibits the in vitro proliferative response of rodent astrocytes to a wide variety of growth factors and cytokines. Although important species differences exist in these glial responses this previously unrecognised property of IFN-P may have implications for reducing astrocytosis and thereby promoting endogenous repair. (C) 1998 Elsevier Science B.V. All rights reserved.