THE AUTHOR TRACES THE HISTORY OF POLYGRAPHY, PROVIDES A PSYCHOPHYSIOLOGIC BASIS FOR POLYGRAPHY, AND DETAILS THE BASIC PRINCIPLES INVOLVED AND THE TEST PROCEDURE. THE VALIDITY AND RELIABILITY OF THE POLYGRAPH ARE DISCUSSED, AS WELL AS ITS LEGAL STATUS. CRITICISMS AGAINST THE USE OF POLYGRAPHY ARE ALSO DEALT WITH IN DETAIL TO PROVIDE AN ARGUMENT FOR OR AGAINST ITS ADMISSION INTO EVIDENCE. A SERIES OF COURT CASES IS DESCRIBED TO INDICATE THOSE IN WHICH POLYGRAPH TESTIMONY HAS BEEN ACCEPTED, AND IN SOME INSTANCES, THE REASONS FOR WHICH IT HAS BEEN REJECTED. THE AUTHOR NOTES THAT SINCE THE 1970'S, THERE HAS BEEN A GROWING TREND TOWARD THE ADMISSION OF POLYGRAPH TESTIMONY OVER THE OBJECTION OF PROSECUTION, AND THAT IT HAS ATTAINED A STATUS IN WHICH IT IS ROUTINELY ADMITTED INTO EVIDENCE ON A STIPULATED BASIS IN MANY JURISDICTIONS. IT IS ANTICIPATED THAT IN THE FUTURE A MUCH GREATER USE WILL BE MADE OF THIS TECHNIQUE AND THAT IT WILL NO LONGER BE NECESSARY TO ESTABLISH A FOUNDATION FOR ADMISSION INTO COURT. TRANSCRIPTS FROM THE HIGHLY PUBLICIZED MY LAI MASSACRE INVESTIGATION ARE APPENDED.