Membrane filtration of natural organic matter (NOM) for drinking water supply is becoming increasingly widespread. Plants especially made for removal of humic substances is different in that removal of the organics themselves is deciding the choice of membrane and the design and operation of the plant. Water sources where this is the case are typically soft surface water in cold climates with high concentration of soluble NOM, especially coloured humic substances. In this paper the technology of this application of membrane filtration will be considered in relation to other drinking water applications where the best plant design are different and where the practical and technical challenges are different. In principle, membranes are well suited to treat the actual types of raw water. But because of fouling problems, the challenges in practical application have been significant. Testing is still going on. Some places, like in Norway, these problems have been solved, at least to reasonable satisfaction, and membrane filtration eventually has proven to give good water quality and stable operation in full scale plants.