The increasing use of magnesium for automotive applications underlines the need for ductile alloys, to make them suitable for safety parts and crash absorbing structures. Because of the lattice structure of magnesium there is only one slip system available at room temperature. To activate additional slip mechanises lithium offers an outstanding possibility by modifying the lattice structure. Light weight has made magnesium-lithium-alloys containing more than 12 wt.% of lithium and having a body-centred cubic lattice an interesting choice for aerospace and military application in the 60's. But a wider use of these alloys did not occur. This paper presents the results of an investigation of the development of hexagonal magnesium-lithium-alloys containing 4 wt.% lithium. Even hexagonal magnesium-lithium-alloys show a significant increased ductility. Lithium modified standard alloys will be presented as well as a development of new alloys. Therefore constitutional examinations have been concentrated on the Mg-rich region of the ternary systems Mg-Li-Al and Mg-Li-Zn. Thermodynamic calculations enabled the construction of ternary phase diagrams, which guided the alloy development. Also the increased formability of magnesium-lithium-alloys in terms of extrusion and rolling operations will be shown.