Some persons who claim to have had near-death experiences (NDEs) fail research criteria for having had NDEs ("false positives"); others who deny having had NDEs do meet research criteria for having had NDEs ("false negatives"). The author evaluated false positive claims and false negative denials in an organization that promotes near-death research and in psychiatric outpatients. The frequency of false positives and negatives varied in samples that differed in prevalence of, and knowledge about, NDEs. The influence of participants' knowledge about NDEs on the findings of near-death research makes it critically important to use standardized criteria for identifying NDEs.