  Semileptonic decays of polarised $\tau$ leptons are investigated. Predictions
for the rate, based on CVC and chiral Lagrangians, are contrasted with
experiments. Predictions for the angular distributions of three meson final
states are given. Emphasis is put on studies in electron-positron annihilation
where the neutrino escapes detection and the $\tau$ restframe cannot be
reconstructed. It is shown that the form factors can be measured in ongoing
high statistics experiments. Of particular interest for the three meson case
are the distribution of the normal to the Dalitz plane and the distribution
around this normal. At LEP these distributions allow for an improved
measurement of the $\tau$ polarisation. Implications are considered for an
experiment where the $\tau$ restframe is reconstructed. It is shown that the
measurement of impact parameters with the help of vertex detectors allows a
full kinematic reconstruction, including the direction of the $\tau$ and the
missing neutrino momentum.
