This was the first Korean national study to evaluate prevalence and correlates of suicidal behavior, and to compare multiple and single attempts. A total of 6510 adults completed face-to-face interviews (response rate, 81.7%) through randomly chosen one-person-per-households. Lifetime prevalence and correlates were evaluated with the Korean version of Composite International Diagnostic Interview (K-CIDI), and a questionnaire to inquire about suicidal behaviors. The lifetime prevalence of suicidal ideation, plan, and attempt in South Korea was 15.2%, 3.3%, and 3.2% (single 2.1% and multiple 1.1%), respectively. Younger age was associated with attempts and more strongly associated with multiple attempts. Attempts were the most strongly associated with mood disorders, especially bipolar disorder, which was more strongly associated with multiple attempts. In conclusion, suicidal behaviors are highly prevalent in Korea, especially in young adults. Bipolar disorder was the most strongly associated disorder with suicide attempts, more with multiple attempts.