  It is shown that additional chiral generations are not excluded by the latest
electroweak precision data if one assumes that there is no mixing with the
known three generations. In the case of ``heavy extra generations'', when all
four new particles are heavier than $Z$ boson, quality of the fit for the one
new generation is as good as for zero new generations (Standard Model). In the
case of neutral leptons with masses around 50 GeV (``partially heavy extra
generations'') the minimum of $\chi^2$ is between one and two extra
generations.

High Energy Physics - Phenomenology