We performed multichannel urodynamics before and after augmentation cystoplasty in 26 patients (11 females, 15 males) to determine which bowel segment is best to achieve a large volume and low pressure reservoir. All 26 patients had a neurogenic cause for their bladder dysfunction. Ileum was used in 14 patients and sigmoid was used in 12 patients. Detubularization was performed in all patients. Capacity improved significantly in both the ileum and the sigmoid group after surgery. When detubularized ileum was used, the maximum amplitude of uninhibited reservoir contractions was significantly improved or eliminated postoperatively. When sigmoid was used, uninhibited reservoir contractions did not significantly improve postoperatively and were, in fact, more common than preoperatively. Despite the detubularization, pressure waves were identified in 15 of the 26 patients postoperatively. There was significant improvement in end filling pressures at capacity (compliance) with both ileum and sigmoid postoperatively. However, end filling pressures were significantly higher in the sigmoid group. In conclusion, good capacity was achieved with both ileum and sigmoid postoperatively. However, ileum provided lower reservoir pressures and better compliance. We feel that urodynamically detubularized ileum is better suited than sigmoid for augmentation cystoplasty in patients with neurogenic bladder dysfunction.