This is the final volume of Heisenberg''s Collected Works. Itcontains his papers on a (nonlinear) unified theory ofelementary particles, as well as his contribution tosuperconductivity and multiparticle production. Especiallyinteresting is the first group of papers, which is splitintotwo sections dealing with, firstly, the formulation ofthe famous nonlinear spinor equation and, secondly,itsapplications. Among others the reader willfind a thoroughdiscussion of Heisenberg''s collaboration with W. Pauli onthese matters. Illuminating annotations to the varioussections in this volume have been provided by H. Koppe, R.Hagedorn and the editors.