Fellutamide A, a tripeptide derivative from Penicillium fellutanum was found to be a potent enhancer of nerve growth factor (NGF) synthesis and secretion in vitro. This compound enhanced production of NGF in L-M cells, rat brain cells, and rat glial cells. The mode of action of this compound was suggested to be different from that of a known NGF inducer, epinephrine, as inducing activities of fellutamide A and epinephrine were additive when they were admixed at the concentration which gave saturation in its respective activity. Furthermore, fellutamide A but not epinephrine induced production of NGF in the rat brain cells. NGF-inducing activity of several tripeptides and other compounds related to fellutamide A was examined.