Inflammatory bowel disease (IBD) is a chronic inflammatory state associated with increased risk of intestinal cancers. The aim of this study is to examine serum concentrations of growth-related oncogene (GRO)α , a cytokine with inflammatory and growth-regulatory properties, in patients with IBD. We measured serum concentrations of GRO-α in 60 patients with ulcerative colitis, 42 patients with Crohn’ s disease, 16 patients with other colitides, 12 patients with colorectal cancer, and 40 normal subjects using an enzyme-linked immunosorbent assay. We then analyzed how the cytokine was related to clinical and laboratory variables. Serum GRO-α concentrations in patients with active IBD were significantly higher than those in patients with quiescent disease, which in turn were higher than those in normal controls. Concentrations in patients with active ulcerative colitis were higher than in patients with active Crohn’ s disease. Analysis of paired serum samples showed a decrease in GRO-α after initiation of therapy. Furthermore, serum GRO-α correlated well with laboratory markers of IBD activity. We conclude that GRO-α may have an important role in development of IBD, and might itself be used as a marker of activity. Manipulation of GRO-α function might prove therapeutically useful. The aim of this study is to examine serum concentrations of growth-related oncogene (GRO) alpha, a cytokine with inflammatory and growth-regulatory properties, in patients with IBD. We measured serum concentrations of GRO-α in 60 patients with ulcerative colitis, 42 patients with Crohn’s disease, 16 patients with other colitides, 12 patients with colorectal cancer, and 40 normal subjects using an enzyme-linked immunosorbent assay We then analyzed how the cytokine was related to clinical and laboratory variables. Serum GRO-alpha concentrations in patients with active IBD were significantly higher than those in patients with quiescent disease, which in turn were higher than those in normal controls. with active ulcerative colitis were higher than in patients with active Crohn’s disease. Analysis of paired serum samples showing a decrease in GRO-α after initiation of therapy. Furthermore, serum GRO-α correlated well with laboratory markers of IBD activity. We conclude that GRO-α may have an important role in development of IBD, and might itself be used as a marker of activity. Manipulation of GRO -α function may prove therapeutically useful.