  We study the possible mixings between gauge vector fields and scalar fields
through their self-energies, arising in models with two Higgs doublets. We
derive the relevant set of Schwinger-Dyson equations and the Ward identities
that compel the longitudinal parts of the field propagators. Linear $(R_{\xi})$
gauge is used and the results are given at all orders in perturbative theory,
and some particular aspects of the one loop case are stressed.
