Ganoderma colossum (Fr.) Baker, a white rot fungus distributed in tropical and subtropical forests, is a rare Ganoderma mushroom belonging to the family Ganodermataceae. In Asia, the fruiting body of G. colossum has been used as tonics or as folk medicine for a variety of illnesses, including malignant diseases. Colossolactone H (colo H) as a new compound was isolated and studied for its anticancer mechanism in human lung cancer H1650 cells. We used microarrays to analyze the gene expression changes upon colo H treatment that helped underlying the molecular mechanism of colo H in H1650 lung cancer cells. The H1650 cells treated with colo H for 12 and 24 h for RNA extraction and hybridization on Affymetrix microarrays.