This report describes current methodologies and best practices used for preparation of a port emission inventory. An emission inventory is necessary for port authorities, those doing business at ports (such as terminal operators, tenants, and shipping companies), state and local entities, or other interested parties to understand and quantify the air quality impacts of current port operations, and to assess the impacts of port expansion projects or growth in port activity. An inventory provides the baseline from which to create and implement emission mitigation strategies and track performance over time. This report focuses on mobile emission sources at ports, including oceangoing vessels (OGVs), harbor craft, and cargo handling equipment (CHE), as well as other land-side mobile emission sources at ports, such as locomotives and on-highway vehicles. For this report we reviewed current information on port emission inventory preparation and summarized the most current practices.