The effect of NGF on [Ca2+]i of mature regenerating oligodendroglial cells was investigated by measuring fluo-3 fluorescence. NGF caused transient increases in [Ca2+]i, which could be inhibited by anti-NGF antibody. The rise in [Ca2+]i was in part due to influx of extracellular Ca2+ since it was markedly attenuated in Ca2+-free solution. It also depended on release of Ca2+ from intracellular stores as tested by prior depletion with cyclopiazonic acid. These results support a role for Ca2+ in the effects of NGF on oligodendroglial cells.