In Japanese larch (Larix leptolepis Gordon), a well-developed suspensor forms during somatic embryogenesis. The suspensor is the essential tissue for development of the embryo proper. In high-cell-density culture, the embryogenic cells proliferate, but no somatic embryos form because suspensor development is suppressed. Previously, we ide.gified vanillyl benzyl ether (VBE) as a novel factor suppressing suspensor development from the high-cell-density conditioned medium (HCM), but the inhibitory effect of VBE was weaker than that of HCM added. Therefore, this study attempted to ide.gify another inhibitory factor in the culture medium. Induction of somatic embryos was performed in a medium containing both VBE and a fraction of each chromatogram extracted from the culture medium. Results of the bioassay showed that a fraction had strong inhibitory activity with VBE, but weak activity without it. By physicochemical analyses of the fraction, 4-[(phenylmethoxy)methyl]phenol was ide.gified as an inhibitory factor of larch somatic embryogenesis.