ACRP Report 7 provides guidance on the most important projects to the airport community for ACRP consideration in the area of hazardous air pollutants (HAPs).  It examines the state of the latest research on aviation-related HAP emissions and identifies knowledge gaps that existing research has not yet bridged.  These gaps and related research needs are then prioritized based on the ability of research in those areas to provide airports a better understanding of the relationship of the type and amount of HAPs being emitted and their impacts.  While the main purpose of this report is to identify key research areas important to the airport community for ACRP consideration, research communities at large will also benefit from this report’s comprehensive analysis of aviation-related HAP research needs.