Erbstatin, a tyrosine kinase inhibitor, is known to induce transient differentiation in rat pheochromocytoma PC12h cells; The authors tested seven newly synthesized stable erbstatin analogues for their ability to induce neurite formation and acetylcholine esterase in PC12h cells. Among the inhibitors tested hexyl 2,3-dihydroxycinnamate most efficiently induced neurite formation in PC12h cells. Although this analogue is much more stable than erbstatin, the induction by it was again transient. In addition, the analogue weakly induced acetylcholine esterase activity in PC12h cells. Thus hexyl 2,3-dihydroxycinnamate is a potent inducer of morphological differentiation in PC12h cells.