The medical mushroom Ganoderma lucidumhas long been used and shown effective in Traditional Chinese Medicine for the treatment of many diseases including cancer.The underlying mechanisms however are complex and poorly understood as Ganoderma lucidum contains over hundreds of bioactive compounds.Here we tested the cytotoxic effects of two natural compounds purified from Ganoderma Lucidum,ergosterol peroxide and ganodermanondiol.We found that both compounds exhibited cytotoxicity not only against fast proliferating cells,but also on quiescent,slow-cycling cells.