Background: Use of clinical laboratory test results in diagnostic decision making has become an integral part of clinical medicine. More than 70 % of the most important decisions of medical diagnosis are based on laboratory test results. Present study was aimed to study errors in pre-analytical, analytical and post analytical phases of testing cycle at central clinical laboratory of a tertiary hospital. Material and Methods: Present study was single-center, descriptive, observational study, conducted in department of pathology & biochemistry, at Central Clinical Laboratory