Hahn, S 1999 1999 Recent studies of the strong coupling \as using the DELPHI detector at LEP \cite{pap1,pap2} are reviewed. For the analysis of the data at $ \sqrt{s} = M_Z $ recorded in 1994, a large number of shape observables and their dependence on the event orientation are measured and compared to theoretical calculations in $ { \cal O } ( \alpha_s^2 ) $ . The adjustment of the renormalization scale $ \mu $ turns out to be of major importance. Only a poor description of the data can be achieved if the so-called physical scale $ \mu^2 = Q^2 $ is applied, whereas a combined fit of $ \alpha_s $ and the renormalization scale value yields an excellent description of the high statistics data. For these scale values perfect consistency of the fit values of $ \alpha_s(M_Z) $ is obtained for all event shape observables considered. The running of $ \alpha_s $ is measured from the DELPHI data at $ \sqrt{s} $ = 130 GeV - 172 GeV. Here an analytical power ansatz for the hadronization corrections is compared with hadronization corrections obtained by using Monte Carlo generators.