Two new cytotoxic chromene derivatives, butyrylmallotochromene [10] and isobutyrylmallotochromene [11], were isolated from the pericarps of Mallotus japonicus. The new derivatives were identified as 5,7-dihydroxy-6-(2',4'-dihydroxy-3'-acetyl-5'-methyl-6'-methoxybenzyl)-8 - butyryl-2,2-dimethylchromene [10] and 5,7-dihydroxy-6-(2',4'-dihydroxy-3'-acetyl-5'-methyl-6'-methoxybenzyl)-8 - isobutyryl-2,2-dimethylchromene [11] by means of spectral data. These compounds and their respective acetylation and methylation products were found to be cytotoxic against KB cell lines.