Background: Serum testosterone deficiency increases with aging. Age is also a major risk factor for prostate cancer (PrCa) and PCa tumors are more frequently diagnosed among men >65 years old. We evaluated the relationship between preoperative serum testosterone and clinical/pathological features of PrCa in middle-aged and elderly patients. Methods: A total of 605 PrCa patients who underwent robotic-assisted radical prostatectomy between September 2010 and January 2013 at the University of Pennsylvania, and who had serum testosterone levels measured using Elecsys Testosterone II Immunoassay were included in this IRB-approved protocol. Androgen deficiency was determined as serum free testosterone (FT) <47 pg/ml and total testosterone (TT) <193 ng/dl. Demographic, clinical and tumor characteristics of men with low vs. normal TT or FT were compared using t-test or chi-square tests. Logistic regression was used to determine associations of clinical and pathological variables with FT or TT levels. Results: Among middle-aged men (45-64 years; n = 367), those with low FT and low TT had, on average, a higher BMI (29.7 vs. 27.4, P < 0.01; and 32.2 vs. 27.6; P= 65 years (n = 135) there was no difference in prostatectomy specimens of PrCa between patients with low or normal FT or TT. Conclusion: Among men aged 45e64 years low serum pretreatment FT and TT predicted more aggressive features of PrCa in prostatectomy specimens. In middle-aged patients low testosterone levels measured pre-operatively may indicate more aggressive disease parameters. (C) 2017 Asian Pacific Prostate Society, Published by Elsevier Korea LLC.