Abstract The steam-volatile constituents from ripe fruits of Japanese pepper have been studied using column and gas chromatographic separations, followed by characterization on the basis of infrared, nuclear magnetic resonance, and mass spectrometry. The capillary gas chromatography of the volatile oil from ripe fruits of Japanese pepper revealed the presence of approximately 130 components. Among the components identified were the following: 19 hydrocarbons (α-pinene, camphene, β-pinene, sabinene, myrcene, α-phellandrene, limonene, β-phellandrene, p-cymene, terpinolene, α-copaene, β-caryophyllene, humulene, γ2-cadinene, α-muurolene, δ-cadinene, γ-cadinene calamenene, and α-calacorene), 15 alcohols (linalool, isopulegol, trans- and cis-2,8-p-menthadien-1-o1, terpinen-4-o1, limonen-4-o1, α-terpineol, 1(7), 8-p-menthadien-trans-2-o1, citronellol, trans- and cis-carveol, geraniol, cuminalcohol, β-caryophyllene alcohol, and nerolidol), 9 aldehydes and ketones (citronellal, dihydrocarvone, cryptone, carvone, piperitone, phellandral, cuminaldehyde, perillaldehyde, and piperitenone), 7 esters (isobutyl isovarelate, isobutyl caproate, linalyl acetate, citronellyl acetate, terpinyl acetate, geranyl acetate, and methyl cinnamate), and 6 oxides (1,8-cineol, β-terpinen-3,4-oxide, trans-and cis-limonen-1,2-oxide, terpinolen-4,8-oxide, and methyl chavicol).