X-ray computed tomography, a non-destructive threedimensional imaging tool, has been very helpful in medical diagnosis since the first commercial tomographs were constructed in 1973. In recent years it has gained increasing applications in civil engineering materials research. Several investigators have illustrated the use of computed tomography scans for the non-destructive evaluation of soils and have shown promising applications in characterisation, modelling and computational simulation to optimise asphalt concrete mix design, predict performance and conduct investigative forensic studies. This paper provides a detailed review of X-ray computed tomography applications in characterising asphalt concrete and also describes preliminary studies conducted at the Center for Nondestructive Evaluation (CNDE) at Iowa State University for characterising asphalt and concrete materials using X-ray microcomputed tomography or micro-computed tomography. Researchers are currently using the advanced imaging facilities available at the CNDE to develop a deeper understanding of the pavement internal structure, to develop and optimise the various parameters that describe the internal structure and to relate them to the performance of pavements in a scientific way. This will provide the foundations for building more durable and long-lasting transportation infrastructure systems.