Tissue hypoxia is a well-known stimulus to angiogenesis. The central dead space in healing wounds has been shown to be hypoxic (PO2 = 1 to 10). Angiogenesis is a necessary component of all healing wounds. Rabbit ear chambers were used to explore the contribution of O2 gradients and various inspired oxygen concentrations on wound healing and angiogenesis. These experiments demonstrate that: (1) A hypoxic tissue gradient is mandatory for wound-healing angiogenesis, (2) when the hypoxic gradient is destroyed capillary growth cases, and (3) inspired oxygen concentrations affect the rate and density of capillary growth.