A considerable amount of work has been performed in recent years to utilize piezoelectric materials for semiactive and active-passive hybrid structural damping. Many interesting phenomena have been studied, and promising results have been shown. For semiactive damping, most of the investigations have focused on designing control actions to switch or vary the electrical components in piezoelectric networks. For active-passive hybrid damping, two schools of thought have been examined. One is to use the active and passive features of the piezoelectric materials simultaneously and exercise hybrid damping. The other is to integrate the active piezoelectric materials with traditional passive damping materials into a self-contained hybrid design. The purpose of this paper is to review these efforts, assess the state of the art, and suggest future research directions for semiactive and active-passive hybrid piezoelectric-based damping treatments.