We construct the simplest SO(10) model in which the scale characterizing the coupling of the “invisible axion” is not fixed by the renormalization group analysis to be greater than ≈10 15 GeV. An E 6 model is discussed which also has this property. We also point out that the Peccei-Quinn symmetry cannot be automatic for models based on SO( N) with fermions in the lowest dimensional spinor representations.