It has been recommended previewing test items with the examinee prior to conducting a Concealed Information polygraph Test. This procedure serves to familiarize the suspect with the test items and allows adjustment, if necessary exclusion, of bad test items. According to the National Research Council (2003), however, this procedure could decrease detection efficiency due to habituation. In two experiments using a mock crime paradigm, this possibility was tested. Guilty and innocent mock crime participants were or were not presented with the test items prior to the administration of a Concealed Information Test. No evidence was found that previewing diminishes detection efficiency of the Concealed Information Test. These findings, together with methodological and legal concerns, support the previewing of test items.