The effect hyperoxia had on the hemodynamic response to visual stimulation (black and white checkerboard alternating at a frequency of 8 Hz) of human VI was investigated using a blood oxygenation level-dependent (BOLD) contrast with an fMRI technique. Data were acquired with a 5 on/5 off block paradigm using single-shot gradient-echo echo-planar imaging. Using a two-tailed paired t-test (p < 0.05, n = 13) it was found that the mean percentage signal change and the mean number of activated pixels was significantly increased for hyperoxia (5.7 +/- 0.9, 187 +/- 73, mean +/- SD) relative to those for normoxia (5.4 +/- 0.9, 168 +/- 58). We believe that these results indicate that hyperoxia enhances the activation-induced hemodynamic response in human VI.