Objective: To evaluate rectal sensitivity in patients with pediatric constipat ion (PC) and nonretentive fecal soiling (FNRFS) using pressure-controlled diste ntion (barostat). Study design: Thresholds for rectal sensitivity (first sensati on, urge to defecate, and pain), and rectal compliance were determined using a b arostat. Results: A total of 69 patients with PC (50 males; mean age, 10.9±2.2 years) and 19 patients with FNRFS (15 males; mean age, 10.0±1.9 years) were com pared with 22 healthy volunteers (HVs) (11 males; mean age, 12.7±2.6 years). Se nsitivity thresholds were not significantly different among the 3 groups. Rectal compliance was increased in 58%of the patients with PC (P < .0001 vs HVs). Rectal compliance did not differ between patients with FNRFS and HVs. Children with PC with abnormal rectal function required significantly larger rectal volumes a t urge to defecate. Conclusions: Increased compliance is the most prominent feat ure in patients with PC. Because of higher compliance in these children, larger stool volumes are required to reach the intrarectal pressure of the urge to defe cate. Children with FNRFS have normal rectal function. Objective: To evaluate rectal sensitivity in patients with pediatric constipation (PC) and nonretentive fecal soiling (FNRFS) using pressure-controlled distension (barostat). Study design: Thresholds for rectal sensitivity (first sensati on, urge to defecate, and pain ), and rectal compliance were determined using ab arostat. Results: A total of 69 patients with PC (50 males; mean age, 10.9 ± 2.2 years) and 19 patients with FNRFS (15 males; mean age, 10.0 ± 1.9 years) were Sepsitivity thresholds were not significantly different among the 3 groups. Rectal compliance was increased in 58% of the patients with PC (P <. 0001 vs HVs). Rectal compliance did not differ between patients with FNRFS and HVs. Children with PC with abnormal rectal function required significantly greater rectal volumes at urge to defecate. Conclusions: Increased compliance is the most prominent feat ure in patients with PC. Because of higher compliance in these children, larger stool volumes are required to reach the intrarectal pressure of the urge to defe cate. Children with FNRFS have normal rectal function.