Bisindolylmaleimide VIII (BIM VIII) is a selective protein kinase C (PKC) inhibitor (IC50 = 158 nM for rat brain PKC) that acts at the ATP binding site of PKC. This compound exhibits some degree of PKC isozyme specificity with preference for PKCα over PKCβI, PKCβII, PKCγ, or PKCε (IC50s = 53, 195, 163, 213, and 175 nM, respectively). At 10 μM BIM VIII does not inhibit the tyrosine phosphorylation or the activation of phospholipase C γ1. BIM VIII inhibits carbachol-evoked noradrenaline release from human SH-SY5Y neuroblastoma cells with an IC50 value of 600 nM.