This paper addresses the admissibility under the Federal Rules of Evidence of three types of expert testimony which may involve the admissibility of testimony in the form of legal conclusions. The first type involves testimony embracing an ultimate issue of fact, which the author maintains should be routinely admitted as jurors can determine for themselves whether or not the evidence should be accepted. Testimony in which an expert witness is asked to apply a legal standard or definition to those facts is the second type of evidence. Here, the author concludes that Federal courts should apply the intent of the Federal Rules of Evidence by restricting the admissibility of opinion testimony which could mislead the jury. The final situation considered in this article is where counsel asks experts to express their opinions on substantive law; it is the author's opinion that this type of testimony should be prohibited as it is inconsistent with the role of the trial judge to determine the law and to so instruct the jury. 145 notes