We hypothesized that some of the heterogeneity of pulmonary blood flow present in the normal human lung in normoxia is due to hypoxic pulmonary vasoconstriction (HPV). If so, mild hyperoxia would decrease the heterogeneity of pulmonary perfusion, whereas it would be increased by mild hypoxia. To test this, 6 healthy non-smoking subjects underwent magnetic resonance imaging (MRI) during 20 minutes of breathing different oxygen concentrations through a face mask (normoxia, F_IO₂=0.21; hypoxia, F_IO₂=0.125; hyperoxia, F_IO₂=0.30), in balanced order. Data were acquired on a 1.5T MRI scanner during a breathhold at functional residual capacity from both coronal and sagittal slices in the right lung. Arterial spin labeling was used to quantify the spatial distribution of pulmonary blood flow in ml/min/cm³ and fast low angle shot to quantify the regional proton density, allowing perfusion to be expressed as density-normalized perfusion in ml/min/g. Neither mean proton density (hypoxia, 0.46(0.18) g water/cm³, normoxia, 0.47(0.18) g water/cm³, hyperoxia, 0.48(0.17) g water/cm³, p=0.28) nor mean density-normalized perfusion (hypoxia, 4.89(2.13) ml/min/g, normoxia, 4.94(1.88) ml/min/g, hyperoxia, 5.32(1.83) ml/min/g, p=0.72) was significantly different between conditions in either imaging plane. Similarly perfusion heterogeneity as measured by relative dispersion (hypoxia, 0.74(0.16), normoxia, 0.74(0.10), hyperoxia, 0.76(0.18), p=0.97), fractal dimension (hypoxia, 1.21(0.04), normoxia, 1.19(0.03), hyperoxia, 1.20(0.04), p=0.07), log normal shape parameter (hypoxia, 0.62(0.11), normoxia, 0.72(0.11), hyperoxia, 0.70(0.13), p=0.07), and geometric standard deviation (hypoxia, 1.88(0.20), normoxia, 2.07(0.24), hyperoxia, 2.02(0.28), p=0.11) were also not different. We conclude that hypoxic pulmonary vasoconstriction does not affect pulmonary perfusion heterogeneity in normoxia in the normal supine human lung.