Depression is one of the most significant public health problems in Korea. The lifetime prevalence rates of major depressive disorder (MDD) in Korean adults have ranged from 3.3% to 5.6%, which are lower than those of western countries. Point prevalence rates of MDD in Korean elders from 4.6% to 7.5%, which are relatively higher than those of Western countries and other Eastern countries, have been reported. The prevalence rate of probable depression (depressive symptoms defined by the cutoff point of 16 on the Center for Epidemiologic Studies Depression Scale was lowest in the age group of 40 to 49 years at 7.6%, and highest in the age group of 15 to 18 years at 46.8%. The prevalence of probable depression in Korean elders increased with age and was highest in the group aged 80 years and over, at 35.4%. There is relatively consistent evidence that being female, having low income, no education, prior MDD, dementia and history of cerebrovascular attack increased the risk of depression. Although it is difficult to come to consistent conclusions on the epidemiology of depression in Korea due to methodological differences between studies, depression is already common and will become more common in Korea. Tremendous sociocultural, economic, and political changes along with rapid population aging have contributed and will contribute to the prevalence and impacts of depression in Korea.