Background: Several tumor-suppressor genes have been mapped to chromosome 10q, including PTEN. While loss of 10q is a frequently seen cytogenetic abnormality noted to occur in patients with renal cell carcinoma (RCC), little is known about its prognostic significance. We investigated the association of loss of 10q with pathological features and disease-free survival (DFS) in patients with localized RCC. Methods: All patients from UCLA with primary localized RCC who had tumor cytogenetic analysis were included. Alterations in chromosome 10q was specifically reviewed for this study. Logistic regression analyses were used to assess association of loss of 10q with ISUP grading, and T-stage. Cox proportional hazard modeling and Kaplan-Meier analyses were used to assess the impact of loss of 10q on DFS and OS. Recurrence was defined as any local recurrence or development of new metastasis after surgery. Results: A total of 886 patients were included in this study. Loss of 10q occurred in 68 (7.7%) patients and was more commonly seen in chromophobe subtype (24% vs. 6% in non-chromophobe RCC, p < .0001). Loss of 10q was associated with greater tumor size (mean 6.3 vs 5.1 cm, OR = 1.085 [1.024-1.150], p = .008), T3-stage (37% vs 23%, OR = 1.99 [1.17-3.39], p = .011), and ISUP 3-4 (61% vs 37%, OR = 2.64 [1.58-4.40], p < .0001). On survival analysis, after a mean follow-up of 55 months, these patients had a shorter time to recurrence (Log-rank p = .026) and a worse DFS (HR = 2.15 [1.32-3.50], p = .002) than those without loss of 10q. These findings were confirmed on clear-cell RCC subgroup with also a worse OS (HR = 2.00 [1.09-3.67], p = .026) with an estimated 34% risk of death at 5 years for patients with loss of 10q. Conclusions: Loss of chromosome 10q is a prognostic factor associated with larger tumor size, higher grade and T-stage, and worse survival in patients with localized RCC. Identifying patients with loss of 10q can provide additional prognostic information to clinicopathologic variables.