Membrane-oxygenator performance is limited by the mass-transfer resistance on the blood side. The most successful techniques thus far for enhancing oxygenator performance have employed Liquid-side pressure pulsations. However, this technique is limited since it causes the least relative motion near the membrane. In this study we explore the use of axial vibrations of a membrane tube bundle to increase oxygen transfer to the intralumenal liquid flow. An analytical solution is first developed for the hydrodynamics of laminar flow through a sinusoidally vibrated straight cylindrical tube. This indicates that the effect of the tube vibrations is characterized by a dimensionless velocity and frequency. A novel oxygenator is designed that permits vibrating a parallel membrane hollow tube bundle without directly pulsing the intralumenal liquid flow. An embodiment of this design employing 41 silicone rubber tubes is used to study the oxygenation of water. A tuned response is observed in that the maximum enhancement in mass transfer for a fixed dimensionless vibration velocity occurs at a specific dimensionless frequency. These experiments demonstrate that axial membrane vibrations can increase the mass-transfer coefficient by at least a factor of 2.65, Even greater enhancement may be possible for systems characterized by larger Schmidt or Graetz numbers for which diffusive mass transfer is more limiting. Employing membrane vibrations may offer the additional advantage of minimizing fouling in blood oxygenator as well as other applications.