The flow of suspensions parallel to porous surfaces is typical to engineering and biological systems. In some cases the flow is associated with transfer of mass. This paper considers the effect of the presence of rigid particles near the porous boundary. The kinematic response of the particles to the viscous stresses imposed by the flowing fluid results in streamlines which penetrate the permeable boundary, thus providing a convective enhancement of the rate of transfer. This mechanism is totally absent with boundaries impermeable to flow. The general equations are developed and the important dimensionless parameters are defined. A particular example concerning linear shear flow past a catalytic boundary is evaluated.