Shikonin is a chemically characterized component of traditional Chinese herbal medicine and has been shown to possess antiinflammatory activities. We ascertained that shikonin blocked radiolabelled Regulated on Activation, Normal T cell Expressed and Secreted (RANTES) and macrophage inflammatory protein-1 (MIP-1 α) binding to human monocytes with IC values of 3.58 × 10 and 2.57 × 10 M, respectively. In contrast, up to 1.7 × 10 M of shikonin failed to inhibit stromal cell-derived factor-1 (SDF-1 α) binding to the cells. Additionally, shikonin blocked RANTES and MIP-1 α binding to stable CC chemokine receptor-1 (CCR1) transfected human embryonic kidney (HEK)/293 cells with IC values of 2.63 × 10 and 2.57 × 10 M, respectively. However, shikonin inhibited neither RANTES nor MIP-1 α binding to CCR5 transfected HEK/293 cells. Shikonin also did not inhibit monocyte chemoattractant protein-1 (MCP-1) binding to CCR2 cells, eotaxin binding to CCR3 cells, interferon-inducible T cell α-chemoattractant (I-TAC) binding to CXCR3 cells and SDF-1 α binding to CXCR4 cells. Additionally, shikonin inhibited RANTES-induced CCR1 cell migration, but did not inhibit CCR1 cell migration induced by epidermal growth factor (EGF). Our study suggests shikonin may be a target for the future design of more potent, highly selective therapeutics that could be useful antiinflammatory agents for selectively blocking the binding of CCR1 ligands. © 2001 Published by Elsevier Science B.V.