  The proton-air inelastic cross section value \sigmapairin=338$\pm$21({\it
stat})$\pm$19({\it syst})-28({\it syst}) mb at $\sqrt{s} \approx $ 2 TeV has
been measured by the EAS-TOP Extensive Air Shower experiment. The absorption
length of cosmic ray proton primaries cascades reaching the maximum development
at the observation level is obtained from the flux attenuation for different
zenith angles (i.e. atmospheric depths). The analysis, including the effects of
the heavier primaries contribution and systematic uncertainties, is described.
The experimental result is compared with different high energy interaction
models and the relationships with the {\it pp} ($\bar pp$) total cross section
measurements are discussed.
