목적: Many lines of evidences have suggested that obstructive sleep apnea syndrome (OSAS) is associated with a high incidence of erectile dysfunction (ED). The aim of this study was to investigate the characteristics in OSAS patients with or without ED, and describe the plausible biopsychosocial predictors of ED. 방법:We conducted a longitudinal study of 1,048 patients visiting Seoul National University Hospital for snoring and/or daytime sleepiness from December 2006 to November 2014. Among them, 713 patients, who completed all requirements of questionnaire survey and polysomnographic (PSG) tests, were enrolled in this study. The questionnaire comprised of the Calgary Sleep Apnea Quality of Life Index (SAQLI), the Korean versions of the International Index of Erectile Function questionnaire (KIIEF-5), Beck Depression Inventory (BDI) and Epworth Sleepiness Scale (ESS). 결과:Among 713 patients, 670 (94.0%) patients were diagnosed with OSAS and the severity of OSAS was distributed to mild (141, 21.0%, 15≤AHI<30), moderate (213, 31.8%, 15≤AHI<30) and severe (316, 47.2%, 30<AHI). Most of OSAS patients were middle aged (mean age 45.2) and moderately obese (mean BMI 25.8). Regarding ED, 509 of 670 (76.0%) patients with OSAS had ED. Age showed significant association with ED. The BDI score, SAQLI score and ESS score is an independent predictor of ED in OSAS patents regardless of the severity of OSA (p<0.001). But there was no significant correlation between ED and neck circumference, BMI, blood pressure, ESS or other PSG data (lowest O2 saturation, sleep latency and REM latency). Pearson’s correlation tests were used to evaluate the associations between ED and BDI score, SAQLI score and ESS score. According to our study, ED was positively correlated with BDI score and ESS score and negatively correlated with SAQLI. 결론:Clinicians should consider the possibility of sexual dysfunction and necessity of consultation when their male patients with OSAS showed high depression's severity.