For individuals with end–stage urinary bladder disease, often the only treatment is reconstructive surgery or bladder replacement. Because of the chronic shortage of suitable bladder donors, alternative sources of organs are needed. In this issue, Atala and colleagues describe an approach in which urothelial and smooth muscle cells were harvested from bladder biopsy specimens and seeded onto preformed bladder shaped polymers (pp. 133 and 149). The resultant urinary bladder substitute organs were then tranplanted into dogs whose native bladders had been excised. After only one month, the bladder substitute had developed normal morphology and function, with urinary function maintained for at least 11 months of the study.