During the 1920's, several Japanese psychologists researched electrodermal activity as an indicator of emotions, but World War II interrupted research in lie detection activities. After World War II, the polygraphic method was adopted, modeled after that used in the United States. The Keeler model 302 polygraph was first introduced to Japan in 1953 and served as a pattern for two domestically produced polygraphs introduced in 1955: the YKK polygraph and the TKK polygraph. The Japanese polygraphs were gradually adopted at all prefectural police headquarters. Since 1953, police officers and technical officers have been trained as polygraph examiners at the National Institute of Police Science. Examiner trainees are now selected from university graduates majoring in psychology or other related technical fields. Currently, the peak-of-tension test is preferred in examinations, with the control-question test serving as a supplement. About 4,600 to 4,800 polygraph tests are administered annually in Japan. The polygraph is used by police, the Inspection Bureau of the Postal Service, and the Self Defense Force. The polygraph test in Japan is considered a psychological test or psychological procedure; whereas, in the United States it is used an interrogative technique. Polygraph results have frequently been admitted as evidence in court. Nineteen references are listed.