The performance of membrane extraction in a parallel-plate module arranged, by inserting a vertically impermeable barrier in the flow channel, to create a device of double passes in the raffinate phase, has been investigated. Considerable improvement of mass-transfer rate in a parallel-plate module of fixed dimensions is obtainable if double passes, instead of single pass, are arranged in the phase (raffinate phase or extract phase) where the mass transfer is dominated by its external film and not by the membrane resistance. It is also found that the separation efficiencies are the same for the operations of concurrent-and-countercurrent flow and countercurrent-and-concurrent flow, in a double-pass device.