Chemokines are thought to be important for the recruitment of granulocytes and mononuclear cells and thus for the maintenance of inflammation in ulcerative colitis (UC). We have studied the expression of interferon-gamma inducible protein-10 (IP-10), interleukin-8 (IL-8), monocyte chemoattractant protein (MCP)-1, MCP-3, and macrophage inflammatory protein (MIP)-1alpha in UC patients and control individuals to assess the role of these chemokines in disease progression. Colonic biopsies were taken endoscopically from patients and controls, frozen immediately and subsequently stained for IP-10, IL-8, MCP-1, MCP-3, and MIP-1alpha in serial sections. Cells infiltrating the lamina propria but not epithelial cells express the analyzed chemokines. They were differentiated and counted, and chemokine-expressing cells were quantified by image analysis. The percentage of cells expressing IP-10, IL-8, MCP-1, and MCP-3 was significantly enhanced in all UC samples as compared to controls. Expression in the controls was borderline, except for IP-10. No expression of MIP-1alpha was found in controls and UC. IP-10 was also markedly expressed in the mucosa of control biopsies and therefore could have a role in activated T lymphocytes' recruitment into the healthy mucosa.