We report parallax measurements by the HIPPARCOS satellite of \zeta Puppis and \gamma ^ { 2 } Velorum .
The distance of \zeta Pup is d = 429 ^ { +120 } _ { -77 } pc , in agreement with the commonly adopted value to Vela OB2 .
However , a significantly smaller distance is found for the \gamma ^ { 2 } Vel system : d = 258 ^ { +41 } _ { -31 } pc .

The total mass of \gamma ^ { 2 } Vel derived from its parallax , the angular size of the semi-major axis as measured with intensity interferometry , and the period is M ( WR + O ) = 29.5 \pm 15.9 M _ { \odot } .
This result favors the orbital solution of Pike et al . \markcite p83 ( 1983 ) over that of Moffat et al . \markcite m86 ( 1986 ) .
The stellar parameters for the O star companion derived from line blanketed non-LTE atmosphere models are : T _ { eff } = 34000 \pm 1500 K , \log L / L _ { \odot } = 5.3 \pm 0.15 from which an evolutionary mass of M = 29 \pm 4 M _ { \odot } and an age of 4.0 ^ { +0.8 } _ { -0.5 } Myr is obtained from single star evolutionary models .
With non-LTE model calculations including He and C we derive a luminosity \log L / L _ { \odot } \sim 4.7 \pm 0.2 for the WR star .
The mass-luminosity relation of hydrogen-free WR stars implies a mass of M _ { WR } \sim 5 \pm 1.5 M _ { \odot } .

From our data we favor an age of \sim 10 Myr for the bulk of the Vela OB2 stars .
Evolutionary scenarios for \zeta Pup and \gamma ^ { 2 } Vel are discussed in the light of our results .

\keywords Stars : distances – Stars : early-type – Stars : fundamental parameters – Stars : mass loss – Stars : Wolf-Rayet

Submitted to ApJ Letter