From this brief overview it is possible to discern that MPCPs generally provide energy efficient, predictable mass transfer for contaminant removal from or gas transfer to drinking water. No pressure differential is necessary for provision of a separation of contaminants from water. The very high specific surface area in membrane modules made from hollow fiber membranes allows the transfer to occur in very small process units. Scale-up to full scale is simplified by correlations relating the mass transfer capabilities of a system to its flow characteristics. There has been a great deal of activity in MPCPs in the past few years. MPCPs have been commercialized for several processes and others await commercial application in the drinking water industry. It is expected the interest in these efficient processes will only increase over the years. Membrane processes will not be confined to those driven by maintenance of a high upstream pressure.