A Practice Note examining issues related to the testifying expert's report required by Federal Rule of Civil Procedure (FRCP) 26(a)(2)(B). In particular, this Note includes an overview of the different types of testifying experts and expert disclosures, the required elements of an expert report, rebuttal reports, the timing for disclosing the expert report, sanctions for failing to comply with the disclosure requirements, privilege issues, and a brief summary of the relevant admissibility standards governing expert reports.