Purpose: To determine the effect of transurethral resection on urinary function after permanent prostate brachytherapy using a validated, patient-administered, quality-of-life (QOL) instrument. Methods and Materials: Twenty-seven consecutive brachytherapy patients with clinical T1b-T2b (1997 American Joint Commission on Cancer) prostate cancer and a history of either preimplant or postimplant transurethral resection of the prostate (TURP) were evaluated. Of the 27 patients, I continued to be catheter dependent and was excluded from analysis. Of the remaining 26 patients, each was mailed the urinary function component of the Expanded Prostate Cancer Index (EPIC) and the International Prostate Symptom Score (IPSS). Twenty-six surveys (100%) were returned. The mean and median follow-up was 44.8 and 39.8 months, respectively. The clinical, treatment, and dosimetric parameters evaluated included age, pretreatment prostate-specific antigen level, Gleason score, stage, risk group, prostate volume, presence of diabetes and hypertension, tobacco consumption, number of TURPs, number of grams resected, ultrasound planning volume, hormonal status, supplemental external beam radiotherapy, isotope, follow-up (in months), minimal dose received by 90% of the prostate gland, percentage of prostate volume receiving 100%, 150%, and 200% of the prescribed minimal peripheral dose, and the average and maximal urethral dose. Because baseline IPSSs, but not EPIC scores, were available, a cross-sectional survey was performed in which 51 newly diagnosed prostate cancer patients yet to receive any therapeutic intervention and 195 non-TURP brachytherapy patients served as controls. Results: For all evaluated parameters, superior urinary scores were noted in the preimplant TURP group, with intermediate scores in the postimplant TURP patients and poor urinary QOL scores in the pre- and postimplant TURP patients. With time, the EPIC scores improved in the pre- and postimplant TURP cohorts. In multivariate linear regression analysis of the EPIC urinary summary score, the number of TURPs and supplemental external beam radiotherapy were the strongest predictors for diminished QOL. Conclusion: TURP results in diminished urinary QOL after brachytherapy. However, patients who underwent preimplant TURP had urinary QOL approaching that of non-TURP brachytherapy patients. Significant urinary dysfunction was noted in approximately one-half of patients who underwent postimplant TURP (especially pre-and postimplant TURP). Because most patients with brachytherapy-related urinary obstruction will eventually spontaneously void, TURP should be approached with extreme caution and only after substantial time has transpired. (C) 2004 Elsevier Inc.