Publication bias has a negative impact on the ability of healthcare providers and consumers to make unbiased healthcare decisions. The demand for greater transparency of clinical trials has increased and a prospective registry has been suggested by the International Committee of Medical Journal Editors. By 2008, prospective registration was considered as an ethical requirement within the Declaration of Helsinki. In Korea, the clinical research registry named 'Clinical Research Information Service (CRIS)' was recently established and became a data provider as a primary registry to the World Health Organization (WHO) International Clinical Trial Registry Platform search portal. This means that CRIS conforms to the WHO registry criteria and that registering trials with the CRIS satisfies the trial registration policies of many medical journals. To improve the comprehensiveness and completeness of registered clinical research data, it is necessary to communicate and raise awareness of the need to register clinical trials, as well as to establish national policies on clinical trial registration.