Presenting symptoms and their duration may affect the time that elapses prior to definitive diagnosis of inflammatory bowel disease (IBD). This study was undertaken to determine the mean duration of presenting symptoms and diagnostic lag in children with IBD. The medical records of all patients less than 19 years of age diagnosed with IBD at the pediatric gastroenterology clinic of Children's Hospital of Wisconsin between 1990-1995 were reviewed. The age at diagnosis, gender, presenting symptoms and duration, disease location, and diagnostic lag were analyzed. There were 91 children (49 male) diagnosed with IBD. Crohn's disease (CD) was diagnosed in 58, ulcerative colitis (UC) in 24, and indeterminate colitis in 9. The mean ages at diagnosis were 11.4 years for CD, 9.7 years for UC, and 7.8 years for indeterminate colitis. The most frequent presenting symptoms were abdominal pain, diarrhea, hematochezia, and weight loss. The average lag in diagnosis of CD was 7.1 months, which varied by disease location: small intestine 10.5 months, ileocolonic 7.5 months, and colonic 6.4 months. The average lag in diagnosis was 6.7 months for UC and 14 months for indeterminate colitis. Children presenting with growth failure had the longest diagnostic lag. (a) The elapsed time between symptom onset and the diagnosis of CD has decreased. (b) The diagnostic lag in CD decreases with distal colonic involvement. (c) Following onset of symptoms UC was diagnosed only slightly more rapidly than CD.