Recently proposed models of weak interactions based on spontaneously broken gauge symmetry contain additional interactions arising from exchange of the scalar Higgs particles and/or neutral vector bosons. Further, higher-order corrections are finite, and therefore should be taken seriously. We investigate what constraints on parameters of models are imposed by consideration of Higgs-particle exchange and of higher-order effects in $K$ decays. To bring out the main points we shall focus mainly on the SO(3) models of Georgi and Glashow. In the 5-quark version of the Georgi-Glashow model, the Higgs scalar couples strongly to ($\overline{\lambda }\mathfrak{N}$), and to ($\overline{e}e$), so that processes such as $K^{+}\to {\pi }^{+}+e+\overline{e}$ decay can occur already in lowest order. Thus a stringent lower bound ($m_{\phi }\ge 10$ GeV) is imposed on the mass of the scalar particle. For the process $K_L\to \mu +\overline{\mu }$, which occurs in second order, we find the amplitude to be of order $G_F\alpha {sin\theta }_C$ and independent of the value of $M_W$. This is clearly in contradiction with experiment and rules out the 5-quark version. We analyze also an 8-quark version of the model, in which extra quarks are used to suppress the amplitudes for $K_L\to \mu +\overline{\mu }$ and $K^0\leftrightarrow {\overline{K}}^0$: The amplitudes are of order $G_F\alpha \left(\frac{\Delta m^2}{{M_W}^2}\right)$, where $\Delta m^2$ is the difference between the squared masses of "charmed" and "uncharmed" quarks. It is also shown that in this version single-scalar-particle exchange is altogether forbidden and the constraint on $m_{\phi }$ is accordingly eliminated. Constraints similar to those found for the Georgi-Glashow models also apply to other spontaneously broken gauge models of weak interactions.

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