Summary: A strategy is presented for active damping of structures with guy cables. The active member consists of a piezoelectric actuator collocated with a force sensor. The control algorithm consists of an integral force feedback; it has guaranteed stability, including at the parametric resonance. The results are confirmed by an experiment. Also described is an efficient modeling technique for cable structures; simple and powerful results are established, which permit prediction of the closed-loop poles with a root locus technique. This technique is demonstrated on a guyed truss.