Small systems have special problems when it comes to meeting the requirements of the Surface Water Treatment Rule. Their options include full-scale central treatment, alternative package plants, and point of entry devices. This paper focuses on the use of membranes and their application to small systems for meeting the SWTR requirements-- namely as an alternative to filtration for particle removal. Ultrafiltration and microfiltration have been shown to be very effective for particulate removal, hence these systems have particular application to meeting SWTR treatment needs. System components of membrane filtration include pretreatment, membrane, posttreatment and residual disposal. UF and MF characteristics are described, as are typical operating conditions and membrane construction. Capital and operating costs are related to source water quality; they are broken down into pretreatment, posttreatment, and residual disposal.