Subjects at clinical high risk (CHR) for psychosis have been the focus of clinical attention in psychiatry for the last 15 years, leading to the development of valid and reliable diagnostic instruments to detect these individuals early in the course of their illness. These efforts have resulted in research into optimal preventive measures. Our experiences at and data from the Seoul Youth Clinic support the validity of the CHR concept and its underlying neurobiological basis and provide valuable information related to the determination of appropriate clinical interventions. The limitations of the current criteria for CHR, such as the relatively low transition rates to psychosis and the "false-positive" problem, are also common critical issues in Korea. Additionally, concerns about social stigmatization and the potential side effects of pharmacotherapy render individuals at CHR reluctant to visit clinical settings. Therefore, further investigations using a combination of predictive markers based on clinical and neurobiological studies of those at CHR are needed to refine the diagnostic criteria, overcome their current limitations including ethical issues, and develop phase-specific and individualized therapeutic interventions.