The new rules have produced substantial changes in the way that expert testimony is offered and opposed. With the increased use of expert testimony, practicing trial lawyers should be intimately familiar with the workings of the rules concerned with its admission. They should also be aware that the adoption of the new rules has modified Iowa common law rather than abrogating it. Where a direct conflict exists, the new rules prevail. However, Iowa courts will look to Iowa common law where an ambiguity exists in the newly adopted rules. Like the previous rules, the new rules have three main requirements for the admissibility of expert testimony: (1) the subject matter must be a proper one, (2) the expert must be qualified, and (3) if the underpinnings of the expert testimony are reasonably relied upon they need not appear in the record, but the court may require it. Discussions of specific components of the rules and 191 footnotes.