Nondestructive testing (NDT) of historic structures can be used for architectural archaeology, structural stability analysis, or materials characterization. Four types of physical probes are available: sound, penetrating radiation, visible light, and electromagnetism. Each of these can be utilized in several ways. Additional options involve hybrid techniques that combine probe methods. Widespread application in architectural conservation depends upon overcoming institutional barriers including the lack of standardization, fragmented decision-making, and restrictive contracting procedures that do not take into account the benefits of NDT.