We present the pheomenology of SU(2)/sub L/ x SU(2)/sub R/ x U(1)/sub L/ x U(1)/sub R/ gauge models of the weak and electromagnetic interactions in a simple parametric form, based on the eigenvectors of the intermediate-vector-boson mass matrix. The neutral-current interactions are described in general by four angles and three Z/sup 0/ masses. For natural extinction of atomic physics parity violation, one Z boson has pure vector couplings, the other two pure axial-vector couplings. Imposing equivalence with the neutrino scattering phenomenology of the Weinberg-Salam model, only one parameter remains; this degree of freedom allows an axial-vector Z boson to have low mass. The observable consequences of a light Z/sup 0/ are explored for e/sup +/e/sup -/ annihilation, Drell-Yan production of lepton pairs, deep-inelastic lepton scattering by neutral currents, and the anomalous magnetic moment of the muon. A Z mass as low as 30 GeV is compatible with existing measurements; the most stringent present limit is set by the muon magnetic moment. We estimate a Z/sub 3/(30) signal would be about 10% of the UPSILON (9.5) signal in pp ..-->.. ..mu../sup +/..mu../sup -/X at top CERN ISR energies ..sqrt..s = 60 GeV, and that Z/sub 3/(30) would give a - 13%more » asymmetry in e/sup +/e/sup -/ ..-->.. ..mu../sup +/..mu../sup -/ at top SPEAR energies ..sqrt..s = 7.5 GeV.« less