Objectives: The study was designed to explore whether the credibility of children's statements regarding their alleged experiences of child sexual abuse could be assessed in a more valid and reliable way when investigative interviews were conducted using the NICHD protocol rather than in an unstructured manner. Methods: Forty-two experienced Israeli youth investigators each assessed the credibility of allegations of sexual abuse made by alleged victims of sexual abuse when interviewed either with or without the protocol. Half of the alleged incidents were judged likely to have happened (''plausible'') on the basis of independent evidence, while half were deemed unlikely to have happened (''implausible''). Results: More non-protocol than protocol interviews were rated as ''No judgment possible'' rather than either credible or incredible. Allegations made in protocol interviews were more accurately rated as credible or incredible when they were either plausible or implausible, respectively, than those made in non-protocol statements. Levels of inter-rater reliability were also higher when protocol interviews were rated. The differences were significant only for plausible cases, however. Conclusions: The use of the NICHD protocol facilitated the assessment of credibility by child investigators although incredible allegations (those describing incidents that were unlikely to have happened) remained difficult to detect, even when the protocol was used.