The paper first discusses how to identify an issue in which it will be proper to call an expert to the stand. Case examples illustrate differences in judges' opinions when working under the Federal Rules of Evidence as opposed to New York State which has not enacted the Rules. This section uses the second trial of Alger Hiss to demonstrate how expert testimony and describes a case where the other side's expert was not allowed to testify. The author also reviews Disciplinary Rule 7-109(C) which states that a lawyer's retaining an expert on a contingent basis is an unprofessional act, other problems encountered in obtaining an expert witness, and Kaufman v. Edelstein. Suggestions on using expert testimony in court address qualifying the expert witness, with attention to the ultimate issue rule and certainty of the expert opinion. This discussion emphasizes that trial attorneys must be up-to-date about the Federal Rules of Evidence and use the qualifying process as an opportunity for advocacy. Other areas covered include the issue of the permissible bases of the expert opinion, cross-examination, and arguing the expert's credibility to the jury. The paper has 38 footnotes.