  Deep inelastic scattering data on F2 structure function from various
fixed-target experiments were analyzed in the non-singlet approximation with a
next-to-next-to-leading-order accuracy. The study of high statistics deep
inelastic scattering data provided by BCDMS, SLAC, NMC and BFP collaborations
was carried out separately for the first one and the rest, followed by a
combined analysis done as well. For the coupling constant the following value
\alpha_s(M_Z^2) = 0.1167 +/- 0.0021 (total exp.error) +0.0056/-0.0036(theor)
was found, which in this approximation turns out to be slightly less than that
obtained at the next-to-leading-order, as was generally anticipated. Ditto the
theoretical uncertainties reduced with respect to those obtained in the case of
the next-to-leading-order analysis thus confirming earlier observations.
