Background: Circulating chromogranin A (CgA) levels, a marker for neuroendocrine tumors including carcinoids, have recently been found elevated in some patients with inflammatory bowel disease (IBD), although their significance is unclear. Therefore, we aimed to evaluate CgA levels and their possible relationship with clinical and biochemical disease activity indexes in 119 IBD patients.Methods: The study groups comprised 75 patients with ulcerative colitis, 44 with Crohn's disease, in both active and quiescent phases, and 85 controls.Results: Mean CgA levels were significantly higher in IBD patients than in controls (20.4 ± 14.0 [SD] versus 11.3 ± 4.3 U/L, P < 0.001), without any statistical significant difference among the IBD subgroups. However, CgA levels were above the normal range (20 U/L) in 25/45 patients with active IBD (55%; 95% confidence interval [CI]: 40%–70%) and in 18/74 patients with remission IBD (24%; 95% CI: 15%–36%) (P < 0.001, Fisher's test). Among biochemical parameters, CgA correlated with serum TNF-α levels (rs = 0.398, P < 0.001).Conclusions: High CgA levels can occur in IBD. The disease activity and TNF-α levels seem to influence the CgA pattern, which could reflect the neuroendocrine system activation in response to inflammation. From a clinical point of view, the possibility of high CgA levels in IBD should be taken into consideration when a carcinoid is suspected in such patients, since this event seems to be more frequent than previously considered. Indeed, revision of our 83 patients with gastrointestinal carcinoids, studied between 1997 and 2006, showed that 4 patients had IBD, with a prevalence of 4.8%, which is markedly higher than that of the general population.(Inflamm Bowel Dis 2008)