10601 Background: Conventional renal cell carcinoma (RCC) has a variable natural history, and determining individual prognosis is important to guide management. In this cross-sectional study of RCC, a large number of parameters including hematological and biochemical as well as traditional tumor-related factors have been assessed for their prognostic significance. Methods: Consecutive, unselected patients undergoing nephrectomy for newly diagnosed RCC were invited to participate. Primary end-points were overall survival (OS), disease-free survival (DFS) and cancer-specific survival (CSS). A subset analysis of patients presenting with localized N0 disease was planned. Univariate and multivariate Cox's proportional hazards models were used. Results: 212 patients with RCC formed the study population. Tumor-related factors including grade, stage, presence of necrosis and vascular invasion were prognostic for survival on multivariate testing, in agreement with previous reports. In multivariate analyses pre-operative serum sodium (sNa) was found to be independently and significantly associated with OS and DFS when considered as a continuous variable (see table ). In a further exploratory analysis for all patients when sNa was dichotomized into above/below the median value (139 mmol/l; normal range: 135–145 mmol/l), 3-year OS estimates above and below the median were 74%, 95% CI [64%, 85%] and 54%, 95% CI [44%, 64%]; corresponding figures for 5 years were 68%, 95% CI [54%, 81%] and 44%, 95% CI [33%, 56%]. Conclusions: We have confirmed the prognostic value of traditional tumor-related factors but, to our knowledge, these are the first data to demonstrate that pre-operative sodium concentration may be an important factor associated with survival in patients with RCC. This result suggests that sNa should be considered with established prognostic parameters in modeling survival in RCC. [Table: see text] No significant financial relationships to disclose.