  The symmetry properties of the bosonic string effective action under
Poisson-Lie duality transformations are investigated. A convenient and simple
formulation of these duality transformations is found, that allows the
reduction of the string effective action in a Kaluza-Klein framework. It is
shown that the action is invariant provided that the two Lie algebras, forming
the Drinfeld double, have traceless structure constants. Finally, a functional
relation is found between the Weyl anomaly coefficients of the original and
dual non-linear sigma models.
