We consider extensions of the Standard Model with neutral scalars in multiplets of SU(2) larger than doublets. When those scalars acquire vacuum expectation values, the resulting masses of the gauge bosons W± and Z0 are not related by mW = mZ cos θW . In those extensions of the Standard Model the oblique parameters S and U, when computed at the one-loop level, turn out to be either gauge-dependent or divergent. We show that one may eliminate this problem by modifying the Feynman rules of the Standard Model for some vertices containing the Higgs boson; the modifying factors are equal to 1 in the limit mW = mZ cos θW. We give the result for S in a model with arbitrary numbers of scalar SU(2) triplets with weak hypercharges either 0 or 1.

We present general formulas for the oblique-correction parameters S, T , U , V, W, and X in an extension of the Standard Model having arbitrary numbers of singlet, doublet, and triplet quarks with electric charges −4/3, −1/3, 2/3, and 5/3 that mix with the standard quarks of the same charge.