Deviations from scale invariance resulting from small perturbations of
a general two-dimensional conformal field theory are studied. They ar
e expressed in terms of beta-functions for the renormalization of gene
ral couplings under a local change of scale. The beta-functions for a
homogeneous background are given perturbatively in terms of the data o
f the original conformal theory without any specific assumptions on it
s nature. The renormalization of couplings to primary operators and to
first descendents is considered as well as that of couplings of a dil
atonic type which involve explicit dependence on world sheet curvature
. The first descendent couplings are interpreted as gauge degrees of f
reedom in the string field action and the corresponding gauge transfor
mation is spelled out.