  We establish eigenfunctions estimates, in the semi-classical regime, for
critical energy levels associated to an isolated singularity. For Schr\"odinger
operators, the asymptotic repartition of eigenvectors is the same as in the
regular case, excepted in dimension 1 where a concentration at the critical
point occurs. This principle extends to pseudo-differential operators and the
limit measure is the Liouville measure as long as the singularity remains
integrable.
