Prompted by congressional interest in the Federal Government's use of the polygraph, the National Research Council's (NRC's) report was an exhaustive review of the available scientific evidence on whether the polygraph is a valid tool for assessing a person's credibility. The NRC report not only identified the strengths and limitations of the polygraph, it also considered other existing credibility technologies, namely, brain-wave measurement, voice spectrum analysis, and eye movement; as well as potential future technologies such as thermal image analysis and brain imaging. Regarding an estimate of polygraph accuracy for criminal testing, the NRC could not derive a single statistic to characterize polygraph accuracy. Instead, polygraph accuracy was summarized as a range. For deception testing, a range from 81 percent to 91 percent (median of 86 percent) was determined. For recognition testing, the range was 85 percent to 96 percent (median of 88 percent). Regarding alternatives to the polygraph for credibility assessment, the report concluded that "Some potential alternatives to the polygraph show promise, but none has yet been shown to outperform the polygraph." For each of the existing and future technologies of credibility assessment, this article traces their history, performance to date, and prospects for the future. 1 table and 3 references