Context: Excision of urethral diverticulum in females has been reported to be associated with new onset urodynamic stress urinary incontinence (USUI) in up to 49%. Aims: We have assessed the incidence of new onset USUI in all patients having urethral diverticulum excision with Martius fat pad interposition under the care of a single surgeon between May 1, 2007, and December 1, 2011. The incidence of new onset USUI has been correlated with the preoperative magnetic resonance imaging (MRI) appearance of the urethral diverticulum. Patients and Methods: All 33 patients (mean age 42) having urethral diverticulum with Martius fat pad interposition had prospective data tabulated on demographics, preoperative MRI appearance, and pre- and post-operative videocystometrogram. Statistical Analysis Used: Statistical analysis was performed by Chi-squared and Fisher's exact. Results: Of the 33 patients, 10 (30%) had preoperative USUI and have been excluded from this study. Other preoperative urodynamic findings included idiopathic detrusor overactivity in ten (30%) and bladder outflow obstruction in five (16%). Two (10%) of the patients had a simple diverticulum, 16 (73%) had a horseshoe diverticulum, and 5 (17%) had a circumferential diverticulum. The rate of new onset USUI was 0% for simple, 6% for saddle, and 20% for circumferential. Conclusions: New onset USUI occurs in 9% of patients having excision of urethral diverticulum with Martius fat pad interposition. The incidence appears to increase with increasing complexity of urethral diverticulum on preoperative MRI – rising from 0% following simple urethral diverticulum excision to 20% following circumferential diverticulum excision.