Today's powerful computer workstations enable multimodal nondestructive testing (NDT) to be used for such practical applications as detecting and evaluating defects in structures. Radiography (x ray) and ultrasonics (UT) are examples of two different nondestructive tests, or modalities, which measure characteristics of materials and structures without affecting them. Traditionally, NDT produced an analog result, such as an image on x-ray film, which was difficult to review, interpret, and store. New and more powerful digital NDT techniques, such as industrial x-ray computed tomography (CT), produce digital output that is readily amenable to computerized analysis and storage. Computers are now available with sufficient memory and performance to support interactive processing of digital NDT data sets, which can easily exceed 100 megabytes. Numerous data sets can be stored on small, inexpensive tape cassettes. Failure Analysis Associates, Inc. (FaAA) has developed software-based techniques for using NDT to identify defects in structures. These techniques are also used to visualize the NDT data and to analyze the structural integrity of parts containing NDT-detected defects. FaAA's approach employs state-of-the-art scientific visualization and computer workstation technology. For some types of materials, such as advanced composites, data from different NDT modalities are needed to locate different types of defects. Applications of this technology include assessment of impact damage in composite aerospace structures, investigation of failed assemblies, and evaluation of metallic casting defects.