The application of fracture mechanics to polymers and composites allows the quantitative description of the toughness behaviour by means of fracture mechan­ ics parameters and enables preventive failure analysis. In recent years this young scientific discipline has developed rapidly, and now the experimental results are looking for more applications in industrial practice. However, the practical appli­ cations of fracture mechanics parameters to structural-integrity assessment are severely restricted owing to their limited transferability from specimens to com­ ponents. Indeed, geometry-independent fracture mechanics parameters are very important for the reliable functioning of polymers and components in nearly all industrial application fields. These application fields include the polymer development, quality control, con­ struction and polymer-specific design of reliable components in the motor indus­ try, the electrical industry and the manufacture of household appliances, as well as applications in information technology and medical applications. The present status report on the deformation and fracture behaviour of polymer materials was composed on the basis of revised lectures presented at the Merse­ burg discussion conference entitled 'Deformation and Fracture Behaviour of Polymers' and additional single contributions. The editors and authors have tried hard to present information about the applied fracture mechanics of polymers and composites in the light of their current re­ search work.