Among the lipophilic extracts of seven traditional edible mushrooms, the acetone extract of Sarcodon aspratus markedly inhibited the growth of HL60 human leukemia cells and induced apoptosis after 24 h incubation. The major active component was identified as ergosterol peroxide by NMR and ESI-MS analysis. Ergosterol peroxide completely inhibited growth and induced apoptosis of HL60 cells at a concentration of 25 microM.