The ideal biomaterial for bladder tissue engineering remains elusive. Silk has been utilized in vascular and orthopedic applications, and possesses physical and biological properties well suited for urologic applications. We hypothesize that silk scaffolds can be utilized for bladder tissue engineering.Silk fibroin solution from Bombyx mori silkworm cocoons were woven into patches using gel spinning. Bladder augmentations were performed in 25 CD-1 female mice with non-cell seeded silk, PGA, or SIS patches (0.5 cm2). Sham procedures of cystotomy only were performed. Postoperative assessment at 1, 3, 6, and 10 weeks included: 1) voiding stain on paper (VSOP) testing for qualitative and quantitative assessment of voiding, 2) ultrasound to assess bladder and renal appearance, 3) pathological analysis including Masson trichrome and immunofluorescence of smooth muscle (alpha actin) and urothelial (uroplakin IIIa) markers, and 4) Urodynamics (bladder capacity, voided volume, urinary flow rate, and bladder compliance). Statistical analysis was performed by ANOVA with post-hoc Bonferroni testing.VSOP revealed normalization of voiding pattern in silk-augmented mice at 1 week that persisted to 10 weeks. Renal and bladder ultrasound demonstrated normal kidneys and gradual bladder remodeling over 10 weeks. Histological analysis of silk-augmented bladders revealed complete organized bladder tissue formation without fibrosis around the silk scaffolds by 10 weeks. The new tissue stained robustly for alpha actin (Figure 1) and uroplakin IIIa (Figure 2). 10 weeks after augmentation, mean capacity of silk-augmented bladders was 207 (mcL) v. 51 for controls (p<0.0001). Mean compliance for silk-augmented bladders was 12.0 (mcL/cm H2O) v. 8.4 for controls (p=0.023), 3.9 for PGA-augmented bladders (p=0.0001), and 5.5 for SIS-augmented bladders (p<0.0001).Unseeded silk scaffolds promote formation of organized and functional bladder tissue in mice. In addition, silk produces superior compliance compared to conventional biomaterials. This represents a new option for urologic tissue engineering applications.