In 1993, the U.S. Supreme Court set forth the standard for determining the admissibility of expert scientific evidence in litigation. This standard is known as the Daubert criteria, named after the pertinent case, Daubert v. Merrell Dow Pharmaceuticals, Inc. The Daubert criteria require the courts to determine whether an expert's testimony reflects scientific knowledge, whether his/her findings are derived by the scientific method, and whether the work product is based on good science. The Daubert criteria are especially important in radiation litigation because issues involving radiation doses and effects are often complex and thus a jury will typically rely heavily on the analysis and opinions of experts. According to the Daubert criteria, scientific opinions must be based on a methodology that has a valid, testable hypothesis; has been subject to peer review; and is generally accepted in the scientific community. Additionally, the expert must be qualified to present opinions based on the methodology. Although the application of the Daubert criteria in radiation litigation is highly dependent on the specific court and judge presiding over the case, there have been recent high-profile cases in which application of the criteria has resulted in the dismissal of analysis and opinions offered by scientific experts. Reasons for the dismissals have included basic scientific errors such as failure of the expert to consider all possible explanations for an observed phenomenon, the selective use of data by the expert, and the failure to acknowledge and resolve inconsistencies between the expert's results and those of other investigators. This paper reviews the Daubert criteria as they apply to radiation litigation and provides examples of the application of the criteria from recent judgments involving the Three Mile Island and Hanford Downwinders cases.