Specific therapies in the management of acute pulmonary failure remain elusive, with attention being focused instead on novel supportive measures. The benefits of extracorporeal gas exchange support remain uncertain, and the perceived simplicity of intravascular gas exchange has, therefore, attracted much interest. Initial clinical experience with the intravascular oxygenator (IVOX) device confirms its safety and simplicity, but estimated mean gas-transfer values represent only 25% of basal gas-exchange requirements. The inherent limitations of IVOX as an oxygenator are discussed, providing a rationale for considering IVOX as primarily a CO2 removal device. Reappraisal of the clinical place of intravascular gas exchange and the identification of specific applications most likely to yield benefit to patients are suggested. Design modifications enhancing efficacy are anticipated, further strengthening the potential of intravascular gas-exchange devices in selected patients with pulmonary failure.