Laboratory data are very important in the diagnosis of diseases. The correct interpretation of laboratory data would help clinician to rule in or rule out the diagnosis. For the appropriate interpretation of laboratory tests, the diagnostic accuracy of the tests should be known. One of the important responsibility of Clinical Biochemists is the consultation service to clinicians in requesting of tests or in the interpretation of the test results. Performance characteristics of the tests are important in screening of healthy people for a possible disease or diagnosis and monitoring of the disease. Using sensitive and specific tests would be very heplful in proper diagnosis. However, even though we use sensitive and specific tests, the benefit of these tests would be limited if they were used in low prevalence diseases. For this reason, pretest possibility of a disease would affect the success of a diagnostic test which is used in a given population. In this review, knowledge about the evaluation of the performance characteristics of the diagnostic tests were assessed.