Present status of the Bonn potential and its application in nuclear matter

It is argued that the present situation in nuclear matter requires an explicit description of the 2π-exchange contribution to the NN-interaction providing the intermediate-range attraction. Especially, a realistic treatment of isobar degrees of freedom is strongly suggested. A suitable scheme is described, which starts from a field-theory Hamiltonian and uses old-fashioned perturbation theory consistently in the two- and the many-body problem. Numerical results (for NN-scattering data and nuclear matter binding) emerging from such an approach are briefly outlined. (orig.)