: Bladder cancer is the fourth most common cancer among males and the twelfth most common cancer among females in the United States. It is also the most expensive cancer to treat on a per patient basis. Disparities in bladder cancer recurrence, progression and survival have been reported by patient sex, race/ethnicity, and age. Quality gaps and treatment inequity may contribute to outcomes disparities. In contrast to immutable factors such as genetic or anatomic characteristics, treatment inequity represents a modifiable factor. Thus, our study will identify quality gaps in bladder cancer care and elucidate treatment disparities in order to inform future quality improvement interventions. Effective treatments for bladder cancer exist but may be underutilized at all stages of diagnosis. Treatments include the use of intravesical chemotherapy within 24 hours of the initial transurethral resection of bladder tumor and use of neoadjuvant chemotherapy with radical cystectomy. Failure to use intravesical chemotherapy immediately post-tumor resection (and thus to prevent tumor recurrences) has been estimated to cost the United States around $20 million annually. Increasing the use of guideline-consistent care thus has the potential to improve patient outcomes and reduce disparities while also decreasing healthcare costs. Treatment disparities across patients group have been observed, although findings have not been consistent. Most studies have not comprehensively evaluated bladder cancer care but instead have focused on a few treatment practices, and existing research also may not reflect contemporary treatment patterns. We propose to comprehensively evaluate bladder cancer treatment overall and by patient sex, race/ethnicity, age (Aim 1) and calendar time (Aim 2) in order to identify quality gaps and treatment inequities. Our research team includes an epidemiologist, health economist, two urologists, and a biostatistician/analyst. We will create a retrospective cohort of all patients age 21 years or older diagnosed with bladder cancer during 2001- 2013 within the large, diverse, community-based membership of Kaiser Permanente Southern California (KPSC). We will use our high-quality cancer registry and rich electronic health record to evaluate care among over 9,000 bladder cancer patients. Treatment practices will be coded as yes/no to indicate adherence to well-established treatment recommendations. Multivariable logistic regression models will be used to evaluate differences in treatment adherence across patients groups. Poisson regression or Auto-Regressive Integrated Moving Average (ARIMA) models will be employed to evaluate treatment practices over time. The completion of these aims will provide a detailed comparison of recommended and actual treatment practices by patient sex, race/ethnicity, age, and calendar time for a wide range of bladder cancer treatment recommendations. Future quality improvement efforts may build upon the results to target the treatment gaps with the greatest potential to reduce disparities and improve care delivery and patient outcomes.