Segmental posttensioned bridges are major structures that carry significant traffic. Recent investigations of these bridges identified voids in their ducts. The exposed strands at these void locations can undergo corrosion. The corrosion of strands may lead to the failure of tendons. As such, an effective inspection process for identifying these voids is needed. From a literature review, several nondestructive testing methods are compared for applicability to void inspection in external tendons. The impact echo, ultrasonic pulse velocity, and sounding inspection methods are then selected and assessed for further preliminary testing. The sounding inspection method is further assessed for its effectiveness in identifying voids in a full-scale, external tendon system. The results indicate that sounding inspection slightly underestimates the size of the voids. However, the inspected size and locations of voids have a close correlation with actual voids in ducts. Thus, sounding inspection can be an effective tool for identifying voids because of its easy application in the field.