BACKGROUND: Communication with clinicians in the pre- and post-analytical period to report correct and adequate laboratory test results is crucial. Specifically, the notification of critical values that identify a treatable life-threatening condition should be effectively implemented. Although critical value reporting consists of a series of inter-dependent decisions and processes, standard critical value practices in clinical laboratories have not been agreed upon yet. METHODS: We analyzed the critical value reporting protocols currently used in Korea and performed a systematic review of published literature to provide best practices to improve the quality of critical value reports. RESULTS: Commonly included critical value reports (number of healthcare facilities) are such as followings: hemoglobin (59/59), platelet (52/59), white blood cell (51/59), activated partial thromboplastin time (45/59), glucose (56/59), potassium (55/59), sodium (50/59) total calcium (42/59), creatinine (42/59), and gram stain result when blood culture is positive (24/59). CONCLUSIONS: Substantial variations in the critical value report protocols exist among the participating clinical laboratories. Further effort should be invested to standardize the protocol.