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BACKGROUND The utility of renal mass biopsies (RMB) in the diagnosis of kidney tumors remains debatable. OBJECTIVE To assess patient and urologist preferences regarding the utilization of RMB. DESIGN, SETTING, AND PARTICIPANTS Seventy-three patients diagnosed with renal tumors and 59 board-certified urologists were asked to participate in an interview-based study. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS Using the standard gamble method we determined the minimal accepted accuracy at which RMB would be favored as part of the diagnostic process. Clinical and demographic data with potential to affect participants' preferences were analyzed. RESULTS AND LIMITATIONS At the time of the study interview, 56 patients (77%) were referred for kidney surgery and 17 (23%) opted for surveillance. Overall, 59% of the patients accepted some level of inaccuracy (1-20%), whereas 27% refuted a biopsy. Anxiety associated with the possibility of missing cancer was the primary determinant (82%) for declining RMB among patients referred for surgery, while fear of complications was the primary reason (58%) among those undergoing surveillance. Having an academic degree was associated with a lower accuracy threshold (p=0.03). Of the 59 participating urologists, 39% were reluctant to recommend RMB, primarily because of its inexorable nondiagnostic rate. CONCLUSIONS Most patients and urologists would favor RMB to facilitate their definitive treatment decision. Diagnostic accuracy of 95% was acceptable by the majority of study participants. The utility of RMB as part of the diagnostic algorithm for renal tumors should be discussed with patients, emphasizing its potential benefits and limitations. PATIENT SUMMARY Although needle biopsy seems to be an effective tool to differentiate benign from malignant kidney lesions, it is not commonly used. Our study shows that most patients would opt for a biopsy before definitive treatment decision despite its imperfect accuracy. Hence, the option of undergoing renal biopsy should be discussed with all patients diagnosed with small renal tumors.