Experiments were performed to study the laminar flow characteristics and the laminar-turbulent transition in a parallel-plate channel, one of whose bounding walls is a porous medium. The flow regime investigated herein is characterized by parallel, unidirectional, fully developed flows in the channel and the porous medium. The experimental results for the laminar regime were found to be in excellent accord with theoretical predictions based on a model which admits a slip velocity at the surface of the porous material. The effect of the presence of the porous wall is to increase the mass flow and decrease the friction factor relative to the corresponding quantities for a solid-walled channel. In addition, transition to turbulence occurs at a lower Reynolds number owing to the presence of the porous wall.