Various nondestructive methods for determining the condition of wooden panel paintings have been investigated. Methods are being developed to detect voids, hidden cracks, and fine fractures that are often a source of premature failure in such objects. Computer analysis shows that cracks in wood promote severe stress concentrations which are aggravated by the mechanical constraints imposed on the wood by the construction of a panel painting. The panel's structural condition needs to be mapped in a nondestructive fashion in order to predict how these objects will mechanically respond over time or in different environments. Decisions can then be made ad to whether an object can be safely removed from storage, if it can withstand conservation treatment, if it can be continuously displayed, or if it can be safely shipped to special exhibitions. We have demonstrated the NDE capabilities of different techniques by examining standard panels of white oak, tulip poplar, hard maple, true mahogany, black cherry, and western pine. The panels contain voids between 0.15 and 0.6 cm in diameter and cracks smaller then 0.02 cm. The techniques for investigation included x-ray radiography, xeroradiography, and ultrasonics. Results show that both x-ray radiography and xeroradiography techniques can easily find voids at least as small as 0.15 cm. Xeroradiography has its benefits over x-ray radiography because its edge enhancement property enables flaws to be displayed prominently. At certain angles, cracks less than 0.02 cm were easily seen. The results of using these two techniques on a panel painting are discussed. Ultrasound techniques using an all-air coupled system and a hybrid air-coupled/dry-coupled system have shown promising preliminary results for finding coils and cracks.