['To investigate whether diabetes mellitus (DM) was associated with postoperative outcomes, including prostate-specific antigen doubling time, among men who underwent radical prostatectomy (RP) for clinically localized prostate cancer (PCa).', 'Data of 661 patients who underwent radical prostatectomy for node-negative prostate cancer and were followed up for ≥3 years postoperatively at our institution were analyzed. Associations between diabetes mellitus at surgery and outcomes following radical prostatectomy, such as biochemical recurrence-free survival and prostate-specific antigen doubling time, were examined. Aggressive recurrence was defined as biochemical recurrence with prostate-specific antigen doubling time <9 months.', 'Of the 661 total subjects, DM (n = 67, 10.1 %) and non-DM group (n = 594, 89.9 %) showed no significant differences in various clinicopathologic parameters including age and PSA. DM group had lower postoperative biochemical recurrence-free survival than non-DM group, with observed difference approaching statistical significance (log-rank, p = 0.077). On multivariate analysis, DM at surgery was significantly associated with aggressive recurrence following RP (p = 0.048). Pathologic Gleason score (p = 0.008) and seminal vesicle invasion (p = 0.010) were also significantly associated with aggressive recurrence on multivariate analysis.'] Is diabetes mellitus associated with short prostate-specific antigen doubling time after radical prostatectomy?