Background and aims: The clinical course of inflammatory bowel disease is cha racterised by a succession of relapses and remissions. The aim of our study was to assess whether the predictive value of faecal calprotectin, a non- invasive marker of intestinal inflammation, for clinical relapse is different in ulcera tive colitis (UC) and Crohn’ s disease (CD). Methods: Seventy nine consecutive patients with a diagnosis of clinically quiescent inflammatory bowel disease (38 CD and 41 UC) were followed for 12 months, undergoing regular clinical evaluati ons and blood tests. A single stool sample was collected at the beginning of the study from each patient and the calprotectin concentration was assessed by a co mmercially available enzyme linked immunoassay. Results: In CD, median calprotec tin values were 220.1 μ g/g (95% confidence interval (CI) 21.7- 418.5) in th ose patients who relapsed during follow up, and 220.5 μ g/g (95% CI 53- 388) in non- relapsing patients (p = 0.395). In UC, median calprotectin values were 220.6 μ g/g (95% CI 86- 355.2) and 67 μ g/g (95% CI 15- 119) in relapsi ng and non- relapsing patients, respectively (p< 0.0001). The multivariate Cox (proportional hazard) regression model, after adjustment for possible confoundin g variables, showed a twofold and 14- fold increase in the relapse risk, respec tively, in those patients with CD and UC in clinical remission who had a faecal calprotectin concentration higher than 150 μ g/g. Conclusions: Faecal calprotec tin proved to be an even stronger predictor of clinical relapse in UC than in CD , which makes the test a promising non- invasive tool for monitoring and optimi zing therapy. Background and aims: The clinical course of inflammatory bowel disease is chacterised by a succession of relapses and remissions. The aim of our study was to assess whether the predictive value of faecal calprotectin, a non-invasive marker of intestinal inflammation, for clinical relapse are different in ulcera tive colitis (UC) and Crohn’s disease (CD). Methods: Seventy nine consecutive patients with a diagnosis of clinically quiescent inflammatory bowel disease (38 CD and 41 UC) were followed for 12 months, undergoing regular clinical evaluati ons and blood tests. A single stool sample was collected at the beginning of the study from each patient and the calprotectin concentration was assessed by a co-commercially available enzyme linked immunoassay. Results: In CD, median calprotec tin values ​​were 220.1 μg / g (95% confidence interval (CI) 21.7-418.5) in patients who relapsed during follow up and 220.5 μg / g (95% CI 53-388) in non-relapsing patients (p = 0.395) median calprotectin values ​​were 220.6 μg / g (95% CI 86- 355.2) and 67 μg / g (95% CI 15-119) in relapsi ng and non-relapsing patients, respectively (p <0.0001). The multivariate Cox (proportional hazard) regression model, after adjustment for possible confoundin g variables, showed a twofold and 14-fold increase in the relapse risk, respectrively, in those patients with CD and UC in clinical remission who had a facal calprotectin concentration higher than 150 μ g / g. Conclusions: Faecal calprotec tin proved to be even more predictor of clinical relapse in UC than in CD, which makes the test a promising non- invasive tool for monitoring and optimi zing therapy.