Additive manufacturing (AM) presents unique challenges to the nondestructive testing community, not least in that it requires inspection of parts with complex forms that are not possible using subtractive manufacturing. The drive to use AM for parts where design approaches include damage tolerance and retirement-for-cause with high quality and where safety criticality imposes new QA/QC requirements is growing. This article reviews the challenges faced to enable reliable inspection and characterization in metal powder-based AM processes, including issues due to geometric and microstructural features of interest, the limitation on existing and emerging NDT techniques, and remaining technology gaps. The article looks at inspection from powder to finished part, but focuses primarily on monitoring and characterization during the build. In-process, quantitative characterization and monitoring is anticipated to be transformational in advancing adoption of metal AM parts, including offering the potential for in-process repair or early part rejection during part fabrication.