INTRODUCTION: Given that regular nocturnal erections are physiological, it has been suggested that erections are pivotal to the maintenance of erectile tissue health. It has been postulated that a critical element to erectile tissue protection is cavernosal oxygenation. It is accepted that the corpora cavernosa are oxygenated fully during a rigid erection. However, it remains unknown what degree of penile rigidity is required to achieve cavernosal oxygenation at the arterial level. AIM: This analysis was undertaken to define the correlation between intracavernosal pressure (ICP) and cavernosal oxygen partial pressure (pO(2)). MAIN OUTCOME MEASURES: Cavernosal pO(2) at various ICPs. Methods. The study population was comprised of patients undergoing dynamic infusion cavernosometry (DIC) in the evaluation of erectile dysfunction or prior to penile reconstructive surgery. DIC was conducted with a standard vasoactive agent redosing schedule. One milliliter of corporal blood was aspirated at various ICPs into a heparinized syringe for later pO(2) analysis. Blood was placed on ice immediately and transported to the laboratory upon completion of the DIC. RESULTS: Twenty-one blood samples were analyzed from 13 patients. Mean patient age was 43 +/- 18 years. Blood specimens were collected at an ICP range of 6-90 mm Hg. Mean +/- SD pO(2) was 39 +/- 11 mm Hg at ICP < 10 mm Hg, 87 +/- 3 at ICP 11-20 mm Hg, 89 +/- 6 at ICP 21-45 mm Hg and 96 +/- 13 at ICP > 45 mm Hg. CONCLUSIONS: Significant increases in cavernosal oxygenation occur in the earliest stages of erection at relatively low ICP. These findings suggest that partial erections may be sufficient to oxygenate erectile tissue and protect it from prolonged hypoxia-induced damage.