The effect of an extract of Dalbergiae Lignum and four components that were isolated from the extract on the anticarcinogenic phase II marker enzyme, quinone reductase (QR), was investi-gated. Of the solvent extracts of Dalbergiae Lignum, the CH$_2$CI$_2$ fraction was the most potent in inducing QR activity, with a CD value (the concentration required to double the QR activity) of 29.5 $mu$/mL. The CH$_2$CI$_2$ extract was further separated into six compounds, four of which were identified as 4-methoxydalbergione, latifolin, 4＇,6-dihydroxy-7-methoxyflavanone, and obtusafu-ran. Obtusafuran ［CD ＝ 1.1 $mu$M； chemopreventive index (CI) ＝ 101.9］ and latifolin (CD ＝ 1.7 $mu$M； CI ＝ 154.6) displayed potent QR inducing activity and high chemopreventive indices. Lati-folin and 4-methoxydalbergione were identified as strong DPPH-scavengers with half-maximal free radical scavenging concentrations of 15.9 and 17.2 $mu$M, respectively.