The ability to accurately predict blood flow and mass transport in blood oxygenating devices is critical in the design optimization process. To this end, we explored computational fluid dynamics (CFD) method and implemented a general gas-blood transport model for hollow fiber membrane-based oxygenators. This CFD model was validated using a mini-oxygenator; in addition, it was further tested on a commercially available Medtronic Affinity NT blood-gas oxygenator. The blood oxygenation was modeled as a convection-diffusion process, the membrane fiber bundle was modeled as a porous medium, and the viscous and inertial losses caused by fiber bundle were, estimated by Ergun correlation. Pressure distribution, fluid dynamics, and gas transport in both devices were computationally characterized. A parallel in vitro experimental study was carried out to validate the computational modeling. The CFD predicted results correlated well with the experimental data including distributions of fluid pressure, oxygen partial pressure, and oxygen saturation. It demonstrated that the CFD simulation is a promising approach in the development and optimization of blood oxygenating devices. (c) 2006 Elsevier B.V. All rights reserved.