This research describes the working, benefits and challengers of polygraph tests. Polygraph tests are lie-detecting devices that help ascertain individuals’ honesty based on physiological indicators. The heart rate/blood pressure, respiration, and skin responses are the three indicators measured in the test to assess honest/deceitful behavior. The underlying assumption behind the working of polygraph tests is that the autonomic responses of dishonest individuals are distinctively different from those of honest people because the liars will be more nervous than truth tellers. Control Question Test (CQT), Guilty Knowledge Test (GKT) or Concealed Information Test (CIT) and Neuroscience-Based Advanced Polygraph Tests are the important types of polygraph tests used today. Polygraph tests are used to detect truthfulness of individuals in such important fields as crime investigation departments, national security agencies, and business and industry. However, accuracy of polygraph tests and ethical issues associated with the tests are highly debated.