Mucosal healing is gaining more acceptance as a measure of disease activity in Crohn's disease and ulcerative colitis, and it is also gaining acceptance as an endpoint in clinical trials. Recent publications have correlated achievement of mucosal healing with good outcomes. Currently, there is no validated definition of what constitutes mucosal healing in inflammatory bowel disease. In clinical trials of ulcerative colitis, mucosal healing has been achieved with 5-aminosalicylates, corticosteroids, azathioprine, and infliximab. For Crohn's disease, mucosal healing has been achieved with corticosteroids, infliximab, and adalimumab, and mucosal healing has been maintained with infliximab. Achievement of long-term mucosal healing has been associated with a decreased risk of colectomy and colorectal cancer in ulcerative colitis patients, a decreased need for cortico-steroid treatment in Crohn's disease patients, and a trend toward a decreased need for hospitalization in Crohn's disease patients. Unfortunately, assessment of mucosal healing requires regular use of endoscopy, which is associated with increased costs, patient discomfort, and side effects. Biomarkers such as fecal calprotec-tin, fecal lactoferrin, serum C-reactive protein, and fecal S1 00A1 2 have been shown to correlate with disease activity in ulcerative colitis and Crohn's disease; in the future, these biomarkers might be used as surrogate markers for mucosal healing. Newer clinical trials are incorporating mucosal healing as an endpoint for evaluation of efficacy. However, before mucosal healing will be sufficient to guide therapy, clinicians need a standard definition of mucosal healing and a consistently used, prospectively validated scale with good interobserver agreement.