Heisenberg replies to Pauli's letter about two alternations of proceeding with the theory. He writes about a difficulty in the theory of continuous X-ray spectra and its possible solution.

Heisenberg writes about the Uhlenbeck-Konopinski theory of Beta-spectra and a possible relativistic invariant formulation. He also writes about Bothe's refutation of a paper by Shankland, and about a simple model of a non-linear wave theory without universal constant, except c, containing only a pure number to be identified with e$^{2}$/(h.c.).

Pauli writes on the basis of his Princeton experience to suggest a new approach to problems like that dealt with in Fermi's theory.

Heisenberg replies to Pauli's letter, which convinced him that the infinity of the energy values is unavoidable, and that this is connected with shower production. Probably the whole quantum theory of wave fields is wrong. Neumann's suggestion is a possible way out of the dilemma.

The letter asks a question about a model for neutrinos with Delta-like interaction.

Heisenberg thinks that his description of the lowest state (vacuum) is correct, but he does not yet understand how particles as higher states result from his mathematics.

Pauli replies to Heisenberg's letter of 26th November. He writes about consideration of the possibility of introducing the lattice method for the solution of the impact problem.

Pauli talkes about some calculations on classical diffraction theory in reference to Sommerfeld's work.

Pauli makes some remarks on Heisenberg's latest results, especially properties of the Hamilton-function. He gives some comments on nuclear theory, especially the role of the neutrino-field for nuclear forces.

Pauli makes a short report about his research program and about pair creation.