ABSTRACT: Premature ejaculation (PE) is suspected to be the most prevalent male sexual complaint, and the prevalence of PE is considerably high also in the younger generation. We investigated the PE prevalence based on the Diagnostic and Statistical Manual of Mental Disorders (4th ed text revision; DSM-IV-TR) definition and the risk factors of PE in Korean young men via Internet survey. Subjects (n = 3980) aged from 20 to 59, who performed sexual intercourse more than once a month during the past 6 months were asked to participate in this study. Participants were asked to complete a questionnaire that consisted of questions on general, medical, and sexual history related to ejaculation. A total of 600 subjects were included in this study. PE prevalence was found to be 18.3%. Prevalences were not significantly different across age groups, after excluding subjects with erectile dysfunction (ED). Educational level, marital status and duration, average income, sexual orientation, smoking, alcohol consumption, and circumcision status showed no difference in the PE and non-PE groups. Partners perceived satisfaction rates were 45.0% in the PE group and 63.9% in the non-PE group. Significant differences were found between the PE and non-PE groups in terms of ED, obesity, and depression prevalence. However, multiple logistic regression analysis revealed that the significant risk factors of PE were age and the frequency of conversations with partners about sexual intercourse. This Internet-based study is limited because participants probably represent a selected population of Internet users with non-representative educational and socioeconomic profiles. This study is the first to report the prevalence of both self-reported PE and PE on the basis of the DSM-IV-TR definition in the Korean population. This study demonstrates that PE in Korea is as prevalent as it is in European countries and the United States.