annihilation from 14 to 209 GeV

Results from the study of jets in hadronic final states produced in ee annihilation at √ s = 14 to 209 GeV are discussed. Precise measurements of the strong coupling αS at many points of √ s provide convincing evidence for the running of αS as expected by QCD. Several measurements of the running b-quark mass mb(MZ0) are combined yielding mb(MZ0) = (2.92±0.03(stat.)±0.31(syst.)) GeV and compared with low energy results. Strong evidence for the running of the b-quark mass is found. Experimental investigations of the gauge structure of QCD are reviewed and then combined with the results for the colour factors CA = 2.89 ± 0.03(stat.) ± 0.21(syst.) and CF = 1.30± 0.01(stat.)± 0.09(syst.) and correlation coefficient ρ = 0.82. The uncertainties on the colour factors are below 10% and the agreement with the QCD expectation CA = 3 and CF = 4/3 is excellent.