The authors have identified 37 proteins in the whole-cell extracts from human monoblastic leukemia (U937) cell and macrophage-derived foam cell. The in vitro foam cell model was established by incubating the human U937 cells with oxidized low-density lipoprotein. The global changes in protein expressions between U937 foam cell and normal U937 cells were measured with two-dimensional polyacrylamide gel electrophoresis, and some proteins were trypsin-digested and then identified through tandem mass spectrometry after capillary liquid chromatography separation. Some of the identified proteins were validated via Internet links to the U937 proteomic map provided on the Expasy proteomics server. The experimental data can provide potential markers for atherosclerotic studies.