  Certain spacelike mesonic correlation lengths serve as interesting
theoretical probes for the reliability of perturbation theory in
high-temperature QCD, are directly sensitive to chiral symmetry restoration and
to the axial anomaly, and might also have indirect phenomenological signatures
in idealised heavy ion collision experiments. I review here the weak-coupling
predictions for some of these correlation lengths, to be compared with results
from lattice Monte Carlo simulations.
