X-ray Computerized Tomography (CT) has emerged as a powerful, nondestructive tool to study and quantify the three-dimensional internal structure of HMA. Studies, in conjunction with modeling and computational techniques, have focused on characterization of HMA internal air-void distribution, internal structure evolution during laboratory compaction, damage evolution in specimens during laboratory tests, segregation analysis, forensic investigation of pavements using cores, and the quantification of HMA microstructural properties. The Center for Nondestructive Evaluation (CNDE) at Iowa State University (ISU) has an in-house built high-resolution CT system with customized software for data acquisition, volumetric file reconstruction, and visualization. Preliminary studies were conducted at the CNDE to investigate the capabilities and resolution levels of the imaging systems in studying asphalt materials. Researchers at both ISU and Iowa Department of Transportation are currently using the advanced imaging facilities available at the CNDE and the latest developments in image analysis techniques to develop a deeper understanding of the HMA internal structure, develop and optimize the various parameters that describe the internal structure and relate them to the performance of pavements in a scientific way. This will provide the foundations to building more durable and long-lasting pavements.