Shikonin is a active component isolated from the roots of the traditional Chinese herb Lithospermum erythrorhizon and exhibits multiple pharmacological properties, such as anti-oxidant, anti-inflammatory, and anti-tumor effects. Here, the effects of shikonin on the gene expression of human lymphoma U937 cells were investigated using an Affymetrix GeneChip system. The cells were treated with 100 nM shikonin, and followed by incubation for 3h at 37C. Flow cytometry analysis with Annexin-V and propidium iodide demonstrated that no cell death was observed in the cells at 100 nM shikonin. Of approximately 47,000 probe sets analyzed, many genes that were differentially expressed by a factor 2.0 or greater were identified in the cells treated with the compound.