Normobaric oxygen breathing (NOB) is a proven provocation test useful to assess the in vivo peripheral vascular function, especially by noninvasive technologies (e.g. Laser Doppler flowmetry – LDF and photoplethysmography – PPG). However, the vascular effects of hyperoxia are controversial, and regional differences in vascular reactivity are also known as a major source of inter and intraindividual variability. In this study we aim to characterize the human vascular response in the lower limbs assessed by LDF and PPG, to a 10 min NOB challenge. A group of 10 healthy subjects (mean age 20.9 ± 3.0 years old, both sexes) was selected after informed written consent and submitted to a standardized NOB procedure. Variables included, blood flow, measured on the inferior aspect of both feet toes by LDF and reflection PPG; transcutaneous (tc) O2 pressure measured on the dorsum of one foot only by tc gasimetry; heart rate, calculated by PPG; and respiratory rate and depth by pneumography (PNG). Variables were recorded continuously for 30 min and measured in three phases: (i) for 10 min resting period while breathing room atmosphere, (ii) for 10 min NOB and (iii) for 10 min after, corresponding to recovery. Spectral analysis of the PPG, LDF and PNG signals was performed with both Fourier and wavelet transforms, and their range and maximal amplitude frequency compared. Nonparametric statistics were applied (p<0.05). NOB significantly increased ventilation depth and reduced the respiratory rate evoking hyperoxia, as evidenced by the significant increase in tcpO2. Hyperoxia, in turn, produced two distinct vascular responses – 6 subjects responded with a significant perfusion reduction in both limbs while 4 responded with a significant perfusion increase in both limbs. In both vascular responses the LDF and PPG signals were found to be positively and significantly correlated. Spectral analysis revealed the same frequency amplitude for cardiac activity registered by LDF and PPG. The same coherence was found regarding respiratory activity signals from LDF, PPG and PNG. Significant differences for these bands’ frequency of maximal amplitude could not be found. So these opposite vascular effects registered under these conditions must be related with the modification of myogenic and/or endothelial activity induced by hyperoxia and should be further investigated. The present results confirm the controversy around this issue but also, suggest PPG, a long known accessible technology, as a useful tool to look deeper into vascular function quantification.