A series of 45 patients (31 female) underwent clam enterocystoplasty for urgency and incontinence. The majority had detrusor instability. Prolonged conservative treatment had failed in all cases. Improvement occurred in 71% and those younger than 30 years had better overall results; 29% remained incontinent, with 9% requiring a urinary diversion. Many patients did not achieve maximum benefit until 9 months post-operatively. Surgery had no statistically significant effect on any urodynamic parameter and post-operative complications were common. The operation was performed in either the coronal (19) or the sagittal plane (26); this did not influence results. In general, surgery was found to be technically simpler in the sagittal group and it is recommended that this becomes the standard procedure. We feel that this operation involves major surgery and should only be offered with reluctance.