The purpose of this study was to analyse effects of chromium and/or copper supplementation on immune function in hypercholesterolaemic postmenopausal women. A 2 x 2 factorial research design was used and 40 subjects were supplemented with 0.394 g lactose, 200 microg Cr, 3.0 mg Cu, or 200 microg Cr and 3.0 mg Cu/d for 12 weeks. A significant interactive effect of Cr and Cu supplementation on lymphocyte proliferation was observed with ConA 50 microg/ml stimulation. After 12 weeks of supplementation, ConA-stimulated (50 microg/ml) lymphocyte proliferation was significantly lower when Cu was added to the Cr supplementation group. Moreover, ConA-stimulated (100 microg/ml) lymphocyte proliferation was significantly lower in the Cu supplementation group compared to the Cr supplementation group after 12 weeks of supplementation. These results suggest that Cu blocks enhancement of lymphocyte proliferation by Cr supplementation and that Cu supplementation has potential suppressive effects on the immune function in these subjects.