  Z Oph, HD149757, is an O9.5 Vnn star with a very high projected rotational
velocity (vsini >= 340 km\s). It is also a classical runaway star due to its
high proper motion. We perform a quantitative analysis of its optical spectrum
in order to measure important observables of the star such as its mass,
effective temperature, luminosity and He, C, N, and O abundances. Comparing
these observed values to those predicted by the rotating evolutionary models of
the Geneva group we find that none of the two sets of models is capable of
reproducing the characteristics of the star. Nevertheless, due to its runaway
nature, the reason for this discrepancy may be that the star is not the result
of the evolution of a single object, but the product of the evolution of a
close binary system.
