  We study the infrared behaviour of the two-dimensional Euclidean O(N)
nonlinear sigma-Model with a suitable ultraviolet cutoff. It is proven that for
a sufficiently large (but finite!) number N of field components the model is
massive and thus has exponentially decaying correlation functions. We use a
representation of the model with an interpolating bosonic field. This permits
to analyse the infrared behaviour without any intermediate breaking of
O(N)-symmetry. The proof is simpler than that of the corresponding result for
the Gross-Neveu-Model.
