Mallotus japonicus seeds were separated to cotyledons and seed coat. The lipid content in the whole seed was 45.2%; the cotyledon lipid content was higher than the seed coat content. The main components of seed Toc were α-, γ- and δ-Toc. δ-Toc was found at a higher level in the seed -coat than in the cotyledon. In whole seed lipids the percentages of campe-, stigma- and sitosterols in demethylsterol were 31.1, 10.7 and 58.0, respectively. Clear differences were not found in sterol compositions between free sterol and sterol esters. The main components of monomethylsterol in whole seed lipids were cycloeucalenol (including gramisterol) and 24-ethyllophenol, and the main components of dimethylsterol were cycloartanol, β-amyrin, cycloartenol and 24-methylene cycloartanol.