['To evaluate prospectively the characteristics, erectile function and lower urinary tract symptoms (LUTS) of men undergoing prostate needle biopsy (PNBx).', 'From 2008 to 2011, 134 men were prospectively administered the International Index of Erectile Function (IIEF), American Urological Association Symptom Index (AUA-SI), and quality-of-life (QoL) questionnaires before and after undergoing a single 12-core PNBx. Comparisons of IIEF and AUA-SI scores before and after PNBx, based upon baseline characteristics and prostate cancer (PCa) diagnosis, were performed. Univariable and multivariable logistic regression models were used to characterize predictors of change in IIEF scores.', 'In the 85 men who fulfilled the inclusion criteria, there were no significant differences between the mean (sd) total pre-biopsy and the mean (sd) post-biopsy IIEF scores: 57.8 (12.9) vs 54.3 (17.2). Subgroup analysis showed that men who had biopsy-proven PCa had significantly greater changes in their post-biopsy IIEF scores compared with men without (-10.1 vs. 1.0; P < 0.001). After specific analyses of the IIEF domains in these groups we found significant decreases in every domain, including erectile function (P = 0.01). On multivariate analyses, only PCa diagnosis was associated with a significant change in IIEF (odds ratio 7.2; P = 0.003). There were no differences in AUA-SI or QoL scores in the overall population or in subgroups.'] Is prostate cancer diagnosis associated with an increased risk of erectile dysfunction after prostate biopsy?