Consequences of unitarity and analyticity for weak interactions

One considers the implications of the fact that weak two body scattering amplitudes, when calculated to all orders in any renormalizable model, should exhibit unitary, analytic, ''Mandelstam'' behavior. One discusses from this point of view, the existence of neutral currents, the suppression of ν/sub μ/e elastic scattering, and the possibility of lepton hadron resonances. A brief review is given of the predictions for lepton--lepton scattering of two models in which Mandelstam behavior is explicitly realized. (auth)