Abstract: The Ray-Singer torsion of a closed manifold is a kind of super determinant of the Laplace-Beltrami operator. Its definition is totally analytic in terms of the spectrum of the Laplacian. The Bismut-Zhang theorem computes the Ray-Singer torsion with the help of a Morse-Smale function from the (finite dimensional) Morse complex. In this talk we will generalize this to Morse-Bott-Smale functions. The result is a relation which permits to compute the Ray-Singer torsion of the underlying manifold in terms of the Ray-Singer torsions of the critical manifolds of the Morse-Bott-Smale function field. This is joint work with Dan Burghelea.