This monograph collects research and expository articles reflect- ing the interaction and the cooperation of different groups in several European institut ions concerning current research on mathematical models for the behaviour of materials with phase change. These papers were presented and discussed in a Workshop held at Obidos, Portugal, du ring the first three days of October, 1988, and grew out of a two year period of intensive exploitation of differ- ent abilities and mathematical experiences of the six participating groups, namely, in the University of Augsburg, wh ich was the co-...