Background: HD IL-2 is a standard of care for selected pts with mRCC. Generally objective responses (OR), i.e. complete response (CR) + partial response (PR), of 16-20% are discussed with pts, and not SD. Recent data suggest that cancer immunotherapy may improve survival without inducing OR. Thus, HD IL-2 may provide survival benefit to an additional group of pts not experiencing OR, but only SD as the best response. Methods: All sequential cc mRCC pts treated with HD IL-2 at the University of Utah (1988-2012) were included. Two practitioners independently assessed responses. Best responses were correlated with survival outcomes using Kaplan-Meier analysis. Results: A total of 176 pts (79% male; median age 55 yrs, range 13-76) were included and belonged to the following MSKCC risk categories: 51 (29%) good, 115 (65%) intermediate, and 10 (6%) poor. A CR was identified in 16 (9%), PR in 11 (6%), SD in 52 (30%), progressive disease (PD) in 68 (39%), and not evaluable for response (NE) in 29 (16%) pts. Median overall survival (OS) by risk category for the favorable, intermediate and poor groups was 47.6 (p=0.0005 vs intermediate), 18.0 (p<0.0001 vs poor), and 5.4 (p<0.0001 vs favorable) months (mo), respectively. Table shows correlation of best response with survival outcomes. Conclusions: A clinical benefit of HD IL-2 wasachieved in nearly half of all cc mRCC pts. SD was associated with clinically relevant survival outcomes. There was no statistical difference in outcomes between pts achieving a PR or SD. SD is an important response criterion for treatment with HD IL-2, and may be discussed with pts.