PAIR PRODUCTION OF W BOSONS AT LEP2

We report on the measurements of W pair productions achieved with the 1996 run by the four LEP Collaborations at centre-of-mass energies of 161 GeV and 172 GeV. Combining all possible leptonic and hadronic fina l states, partial and total WW cross-sections are measured and direct measurements of W Branching Ratios are extracted. Finally the W mass i s derived in the framework of the Standard Model profiting from its re markable dependence from the total cross-section at the kinematic prod uction threshold of 161 GeV.