Aqueous extracts and a semipurified fraction obtained by methanol extraction and column chromatography were isolated from Ganoderma lucidum [Ganoderma lucidum (Curtis) P. Karst.; Ganodermataceae Donk] and their effects on interleukin 3-dependent lymphoma cells (DA-1) were studied. Cell viability was reduced by the action of unboiled aqueous extract and by the methanol-extracted column-chromatography semipurified fraction, producing DNA fragmentation in DA-1 cells. Treatments with aqueous extracts showed increments of Bax after 13 h, increments of p53 and Mdm2 after 19 h and a reduction of these three proteins after 24 h. The methanol-extracted semipurified fraction also induced increments of p53 and Mdm2 factors at 19 h with a reduction after 24 h. The methanol-extracted column-chromatography semipurified fraction from Ganoderma lucidum produced minor changes in the level of Akt after treatments for 19 h in DA-1 cells with a slight reduction in the levels of NFkB-p65 factor. Both the unboiled aqueous extract and the methanol-extracted column-chromatography semipurified fraction produced cleavage of inactive caspase 3, as a clear indication of induction of apoptosis by compounds present in Ganoderma lucidum.