Sleep is an ubiquitous phenomenon. It is a developmental product, being subjected to the vicissitudes of human behavior and culture. The author will attempt to elaborate on sleep, sleep disorders, and sleep medicine in Korea from various developmental perspectives (i.e. personal, national and scientific). Korea is a rapidly developing industrialized nation and is now experiencing immense cultural changes which force individuals to change their behavior and value systems. For example, shift working is becoming increasingly popular and early working hours are being adopted by more companies as a measure to win competitions in the international market. In the clinical setting it is observed very easily that patients develop and maintain disturbed sleep-wake rhythm and its consequences. More obstructive sleep apnea, presumably due to obesity, are observed and studied in sleep clinics. The nuclear family system, an inevitable outcome of industrialization, produces some profound difference in sleeping arrangement such as children's earlier separation from parental or grandparental sleeping environment. The question is how these and other industrialization-related changes may affect the incidence and the manifestation of sleep and sleep disorders. In the background there is emerging interest in healthy sleep and sleep disorders, exemplified by increasing coverage of the topics in the mass media and the publication business. Development of sleep medicine/research per se also involves a developmental perspective. Interests in sleep and sleep disorders began sporadically decades ago in Korea and are now actively being organized mainly by the Korean Association of Sleep Medicine and Psychophysiology as a unified developing force. Understanding of sleep and of sleep disorders is not complete without in-depth understanding of culture, philosophy, and tradition from developmental perspectives. Traditional ideas and wisdom from the past are the unavoidable resources for further understanding sleep and developing sleep researches/medicine in Korea as well as in Asia.