It is believed that a chronic state of corporal oxygen desaturation or hypoxemia secondary to the loss of nocturnal erections is a fundamental pathophysiological cause of erectile dysfunction (ED). Limited invasive blood gas measurements in human models have shown decreased oxygen tension in vasculogenic impotence. Normative data on flaccid and erect oxygen saturation (StO(2)) levels are lacking due to the invasive nature of blood gas determinations. Our objective was to determine StO(2) in the flaccid and erect penis in men with and without ED using a tissue oximeter. This FDA-approved instrument provides instantaneous, noninvasive, painless local tissue StO(2) measurements, which highly correlate to blood gas data. The study population included 171 men (18-90 years) who presented to one andrologist. They completed the Sexual Health Inventory for Men (SHIM) based on pharmacologically unassisted erectile function and had penile StO(2) measurements taken. 64 of these men had repeat measurements after PGE-1 induced erections. There are significant differences (P<.001) in corporal and glanular StO(2) in the flaccid (right corpora, 45.23%; left corpora, 52.50%) and erect state (right corpora, 76.58; left corpora, 80.42). Men with ED (right corpora, 45.04% vs 53.58%; P=.02; and left corpora, 50.95% vs 58.78%; P=.03) have significantly lower corporal penile StO(2). Future prospective data collection can correlate penile StO(2) in specific populations, such as diabetics and RRP patients. This may help further elucidate the relationship between corporal hypoxia and the development and progression of ED and possibly its treatment and prevention.