Abstract: The present invention features an apparatus and method for impact-echo testing of structures in situ, in the field. The impact-echo testing method provides a non-invasive, non-destructive way of determining the defects in the structure. The method is both uniform and reliable, the test procedure being substantially identical every time. The apparatus of the invention comprises a portable, hand-held unit having a plurality of impactors disposed therein. The plurality of impactors comprise a number of differently weighted spheres that are each designed to impart a different impact energy into the structure to be tested. Each sphere is disposed on a distal end of a spring-steel rod. A particular weighted sphere is chosen by a selector disposed on the testing unit. The sphere is withdrawn from the rest position by a pair of jaws to a given height above the structure.