Urinary bladder dysfunction is a recognised complication of diabetes mellitus (DM). This is thought to be partly related to altered bladder morphology as DM is associated with increased bladder weight. In DM, increased cellular proliferation is well established. However, there is evidence that in other pathological states affecting the urinary tract, altered apoptosis may also play a role. We therefore used a rabbit model to investigate whether there are any changes in bladder apoptosis with DM. Diabetes was induced in adult New Zealand white rabbits. Age-matched controls were also used. After 6 months, the bladders were excised and weighed. The TUNEL technique was used to detect and quantify apoptosis in both DM and age-matched control bladders. Diabetes was confirmed as this group had significantly (P<0.001) elevated serum glucose-compared to controls. The bladder weights were also significantly (P<0.001) greater in the DM rabbits. Apoptosis was significantly (P<0.001) decreased in the urothelial cells of the DM bladders. Our results confirm previous findings that DM is associated with increased bladder weight. Although this is associated with increased cellular proliferation, we have demonstrated that decreased apoptosis may also play an important role. Therefore, decreased apoptosis may be important in the pathophysiology of DM cystopathy.