Building upon a previous analysis of P v wind lines in LMC O stars , we analyze the P v wind lines in a sample of Galactic O stars which have empirical mass loss rates determined from either their radio fluxes or H \alpha profiles .
Since the wind analysis provides a measure of \dot { M } q where q is the ionization fraction of the ion , we determine q ( P v ) observationally .
In spite of model predictions that q \sim 1 for mid-O stars , we find q ( P v ) \leq 0.15 throughout the O stars .
We discuss the origin of this discrepancy .