One hundred percent oxygen reverses muscle hypoxia in a rat hindlimb model of acute arterial occlusion. Significant morbidity results from extremity ischemia after acute arterial occlusion. Reestablishment of arterial flow is considered to be the ideal treatment, yet substantial tissue loss can occur before this is accomplished. Using a rat hindlimb model we investigated whether the administration of 100% oxygen would decrease tissue hypoxia from acute arterial occlusion. Adult male Sprague-Dawley rats were used, and Po2 recordings were taken from the gastrocnemius muscle by use of an oxygen electrode. Baseline muscle Po2 was recorded, and then the femoral artery was occluded. Repeat recordings were made after 20 minutes of ventilation with room air and after an additional 20 minutes of ventilation with 100% oxygen (N = 10). Control groups consisted of animals undergoing occlusion but continued on room air (N = 3) and animals undergoing sham occlusion but receiving the period of 100% oxygen ventilation (N = 3). Femoral artery occlusion produced a reduction in muscle Po2 from 28.0 +/- 1.4 to 6.1 +/- 2.0 (mean +/- SEM, p less than 0.001). Ventilation with 100% oxygen reversed the tissue hypoxia produced by occlusion (27.3 +/- 2.0, p less than 0.001). The administration of 100% oxygen without femoral artery occlusion resulted in a higher tissue Po2 than the occluded + oxygen group (94 +/- 12 vs 27.3 +/- 2.0, p less than 0.001). Mean arterial blood pressure increased in the experimental group concomitant with the administration of 100% oxygen, but there was no correlation between final blood pressure and final tissue oxygen tension. 