Isovaleramide is isolated from the most active fraction of Valeriana pavonii. Isovaleramide (300 µM) exhibits a 42% of inhibition of the binding of ³H-FNZ to its sites in the in vitro assay. Isovaleramide is without effect at concentrations up to 1000 μM in a variety of in vitro neurotransmitter binding or uptake assays, suggesting that its action does not involve a direct receptor-mediated effect at those systems studied. Isovaleramide (0.15%) induces the formation of nitrile hydratase in Rhodococcus sp. YH 3-3.