Recent results on jet physics and tests of QCD from hadronic final states in
e+e− annihilation at PETRA and at LEP are reviewed, with special emphasis
on hadronic event shapes, charged particle production rates, properties of
quark and gluon jets and determinations of αs​. The data in the entire
energy range from PETRA to LEP-2 are in broad agreement with the QCD
predictions. The world summary of measurements of αs​ is updated and a
detailed discussion of various methods to determine the overall error of
αs​(MZ​) is presented. The new world average is αs​(MZ​)=0.119±0.004. The size of the error depends on the treatment of correlated
uncertainties.Comment: Talk presented at the IVth Int. Symp. on Radiative Corrections,
Barcelona, Sept. 8-12, 1998. 18 pages, 13 eps-figures; uses sprocl.sty and
psfig.st