PNC is a voluntary and conscious effort by a polygraph subject to affect the results of an examination by artificially distorting or interfering with the polygraph recordings. The two types of PNC examined are observable on the polygraph recordings or are evident during the examinations. These are distorting or affecting the normal recording of physiological systems (blood pressure, respiration, and electrodermal responses) and failure to follow the examiner's test instructions. Used in this study were a random selection of 150 polygraph records where PNC was identified by the opinion of the examiner. To determine if PNC is a valid indication of deception, the random cases were divided into two categories: cases in which the examiner was not allowed to interrogate the subject and cases in which the subject was interrogated following the examination. From this second category, a percentage confession rate was calculated to determine how many of the noncooperative subjects were deceptive. PNC was found to be a valid indication of deception if properly diagnosed. Further, properly diagnosed PNC often follows a pattern and is consistent between charts of the same subject. As the chart examples in the study illustrate, PNC is fairly easy to recognize and should be considered during chart interpretation. An examiner should never report as truthful subjects who engage in PNC on portions of the test or throughout the examination. At best, the examiner should give an inconclusive opinion. If PNC is evident on multiple-issue examinations (preemployment or periodic examinations), the examiner's opinion should indicate deception on one or more of the issues under investigation but not on all of the issues. Polygraph charts indicating deception and 12 references are provided.