OBJECTIVE: We hypothesize that children who had pyloric stenosis are at greater risk for developing chronic abdominal pain because this cohort combines various risk factors: an early stressful event, gastric surgery, and perioperative nasogastric tube placement in most cases. STUDY DESIGN: This was a case control study of all children diagnosed with pyloric stenosis during infancy (cases) between January 1, 2000, and June 31, 2005, at Children's Memorial Hospital, Chicago. Because of their similar genetic and socioeconomic backgrounds, siblings aged 4 to 20 years without a history of pyloric stenosis were selected as controls. Parents of children with symptoms completed the parental form of the Pediatric GI Symptoms Rome III version questionnaire for both cases and controls. The primary outcome was the prevalence of chronic abdominal pain, and the secondary outcome was the presence of pain-associated functional gastrointestinal disorder (FGID), in accordance with Rome III criteria. RESULTS: Cases (n = 100; mean age, 7.49 +/- 1.43 years; 29 girls) and controls (n = 91; mean age, 9.20 +/- 4.19 years; 29 girls) participated in the study. Mean time to follow-up was 7.2 +/- 1.6 years. Chronic abdominal pain was significantly more common in cases than in controls (20/80 [25%] vs 5/91 [5.8%]; OR, 4.3; 95% CI, 1.5-12; P = .0045). Seven out of 20 subjects (35%) met the Rome III criteria for diagnosis of a pain-associated FGID (3 with irritable bowel syndrome, 2 with functional dyspepsia, and 2 with functional abdominal pain), and 1 patient in the control group (with irritable bowel syndrome) met these criteria (OR, 6.8; 95% CI, 0.82-56; P = .043). CONCLUSION: We have described a new model to study early life events in infants. Our findings suggest that the presence of pyloric stenosis in infancy and factors involved in its perioperative care represent risk factors in the development of chronic abdominal pain in children at long-term follow-up. This study provides important data to sustain the multifactorial theoretical construct of pain-associated FGID and underscores the importance of early life events in the development of chronic abdominal pain in children.