The relative abundance of /sup 17/O and /sup 18/O is found to be remarkably uniform in the giant molecular clouds of our Galaxy, varying by less than approx.5% between the galactic center and the most distant (approx.12 kpc) sources. This uniformity is seen to reflect the close similarity in the galactic distributions of the processes by which these two isotopes are introduced into the interstellar medium, via novae explosions and mass loss from low-to-intermediate mass stars, respectively.