Eighteen terpenoids (1–18) were isolated fromIllicium merrillianum. Compound1was identified as new compound, and its structure was established by comprehensive spectroscopic analysis and single-crystal X-ray diffraction. All compounds were evaluated for nerve growth factor (NGF)-mediated neurite outgrowth activity using rat pheochromocytoma (PC12) cells as a model system of neuronal differentiation. Compounds1,3,18showed significant neurite outgrowth-promoting activity in the presence of 20 ng/ml NGF in a dose-dependent manner at concentrations of 1–100 μM after 24-h treatment. Subtle difference of functional groups at C-2 position in hopane-type triterpene resulted in enormous bioactivity difference, compound1was neurotrophic but2was cytotoxic. [ABSTRACT FROM AUTHOR]