We aimed to examine correlation of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) with diagnosis of inflammatory bowel disease and with clinical, endoscopic, histological, and radiographic disease activity during follow-up. We reviewed charts of 135 children with inflammatory bowel disease and correlated their ESR and CRP values with disease activity in various encounters during 5 years. Normal ESR and CRP values were observed in up to 28% of children with Crohn disease and 42% of children with ulcerative colitis at diagnosis, respectively. Correlation of ESR and CRP with Crohn disease clinical, endoscopic, and histologic activity during follow-up depended on their value at diagnosis and mode of analysis (continuous or dichotomous). Both markers were not useful in predicting clinical, endoscopic, or histologic ulcerative colitis disease activity and radiographic small bowel Crohn disease during follow-up.