Water shortage problems are becoming more widespread and are encouraging users to treat difficult waters and to value the reuse of wastewater. Membrane processes such as reverse osmosis (RO) have been used to treat such waters as well as sea water (SWRO). The applications, particularly for wastewater, have been limited due to the sensitivity of RO membranes to fouling and the inefficiency of the conventional pretreatment process technologies used. This paper reviews the benefits of wastewater reuse for industrial and municipal applications. It demonstrates how continuous microfiltration (CW) pretreatment to RO can reduce capital and operating costs of RO systems, improve their efficiency and enable reliable operation on a wider variety of water sources. This information is supported by operational data from a number of CMF RO installations worldwide on difficult to treat feed waters.