In the situation where we have a sequence of two spectrum extensions, we de
scribe a spectral sequence converging to the topological Hochschild homolog
y of the top spectrum over the base spectrum, in terms of invariants of the
intermediate extensions. The main application is to the case of topologica
l Hochschild homology of a ring extension, when the base spectrum is taken
to be the sphere spectrum. We get a spectral sequence starting with appropr
iate algebraic Tor groups of the topological Hochschild homology groups of
a ring, converging to the topological Hochschild homology of an algebra ove
r it. (C) 2000 Elsevier Science B.V. All rights reserved. MSC. 19D55; 16E40
; 19D50; 55T99.