SEARCH FOR NEW NEUTRAL BOSONS AT FUTURE COLLIDERS

This is a short review of present and future limits on new neutral gau ge bosons, in particular on hadrophilic or leptophobic Z's recently pr oposed to interpret the observed fluctuations of Gamma(c,b) at LEP. Li ght gauge bosons coupled to lepton number differences or to baryon num ber are also examples of the model dependence of these bounds. The mix ing between the U(1) factors plays an important role in the phenomenol ogy of these extended electroweak models. Future improvements based on the analysis of precise electroweak data are emphasized.