Over many centuries, herbal remedies have treated a variety of ailments. This empiric observational approach has produced a number of leads for formulated medicines. Ganoderma lucidum extract was screened for its anti-proliferative activity using a panel of 26 human cancer cell lines. The six most sensitive hematologic cell lines were: HL-60 (ED50 26 microg/ml), U937 (63 microg/ml), K562 (50 microg/ml), Blin-1 (38 microg/ml), Nalm-6 (30 microg/ml) and RPMI8226 (40 microg/ml). Cell cycle analyses revealed a G2/M arrest, most prominently in HL-60 cells. Four hematopoietic cell lines (HL-60, Blin-1, U937, RPMI8226) were examined for apoptosis, which ranged between 21 and 92%. After exposure to G. lucidum extract, HL-60 cells became multinucleated with an increased DNA content. These results indicate that G. lucidum extract has a profound activity against leukemia, lymphoma and multiple myeloma cells and may be a novel adjunctive therapy for the treatment of hematologic malignancies.