Three-dimensional dynamic imaging using free-breathing oxygen-enhanced (OE) ultrashort echo time (UTE) MRI can measure change of partial pressure of oxygen (ΔPO2) and wash-in/out time constants. Nine healthy subjects underwent the dynamic OE MRI protocol at 1.5T. A subset of 4 subjects underwent repeated exams and 2 of these 4 underwent the same protocol at 3.0T on the same day. The inter-exam variations at 1.5T suggest good quantitative measurements of lung function and wash-in/out dynamics with variations observed in ΔPO2max. The parametric maps imply comparable wash-in/out time constants and normal ventilation measured at 1.5T vs. 3.0T.