The present situation in the determination of αs

Measurements of the strong coupling αs serve as an important consistency test of QCD. The results presented here are based on event shape observables in ee annihilation. But since QCD is the theory of (asymptotically) free quarks and gluons, hadronisation effects need to be accounted for. This is traditionally done either with phenomenological models (“monte carlo”), or with the help of QCD inspired power corrections. But i will also discuss results which indicate, that for inclusive mean values non–perturbative effects are much smaller than originally assumed.