358 Background: Patients treated for urothelial carcinoma of the urinary bladder treated with radical cystectomy and pelvic lymph node dissection have worse clinical outcomes if they receive perioperative blood transfusion. We evaluated the impact of perioperative blood transfusion on oncologic outcomes in patients with upper tract urothelial carcinoma (UTUC) treated with radical nephroureterectomy (RNU). Methods: We conducted a single-center, retrospective review of 405 patients treated with RNU for UTUC. Clinicopathologic characteristics were recorded. Hospital charts were reviewed to determine if patients received perioperative blood transfusion. Characteristics were compared between groups based on transfusion status using Chi-square analyses. Survival was assessed using the Kaplan-Meier method. Cox regression analysis addressed cancer-specific mortality (CSM). Results: Median age was 71.4 years (IQR 63.7-76.5) and the majority of patients were male (64%). Median follow up was 43.4 months (IQR 16.7-86.6). CSM occurred in 26.2% of patients. Perioperative transfusion was associated with higher rates of invasive T stage (>/=T2), (62% vs. 47%, p=0.019) and lymph node positive disease (23% vs. 10.3%, p=0.029). Three year disease-specific survival (DSS) was 80% for the entire cohort. DSS was significantly shorter (p=0.003) for patients receiving transfusion (66.3%, 95% CI 53.7%-76.3%) than those who did not (83.3%, 95% CI 78.3%-87.3%). Transfusion was an independent predictor of CSM on multivariable analysis including gender, grade, invasive T stage, nodal status, and transfusion (Table 1). Conclusions: Perioperative blood transfusion may be associated with adverse pathologic and oncologic outcomes in patients undergoing RNU for UTUC. [Table: see text]