This volume comprises the proceedings of the "3rd International Conference on Distributed Parameter Systems" held at the Chorherrenstift Vorau (Styria), July 6-12, 1986. The aim of the meeting was to stimulate exchange of information between scientists working in the field of distributed parameter systems. The papers included in the proceedings present recent results and most of them include a survey on the background of the problem. Main topics considered in these papers are boundary control for hyperbolic systems, linear-quadratic control problems, robustness, stabilization, visco-elastic and flexible structures, hereditary systems.