[en] Combining neutral current (NC) data in a statistically correct way we determine. (i) the weak NC couplings in neutrino-nucleon and -electron scattering independently of gauge models; (ii) the weak isospin T₃ of the right-handed fermions usub(R), dsub(R) and esub(R)^-, the Z mass, and sin² theta sub(W) in SU(2)xU(1) models with standard left-handed fermion multiplet assignments and two Higgs doublets. Both determinations support the Neinberg-Salam model, although neither considerable right-handed fermion singlet-doublet mixing involving new heavy ferrions can be excluded, nor the existence of a second Higgs doublet. (author)