The presence of numerous organic micropollutants, such as pharmaceutically active compounds (PhACs) and hormones, but also pesticides and industrial pollutants, in the sources for the drinking water supply, are a big concern for drinking water utilities. Even though not all pollutants are harmful to human health, less is known about the consumption of drinking water containing a cocktail of all these solutes. To prevent these pollutants from entering the drinking water, a solid drinking water treatment is necessary. This thesis investigates the removal of, amongst others, pharmaceuticals and hormones by nanofiltration and reverse osmosis membranes. These membranes are currently among the most advanced techniques for removal of organic micropollutants. In the thesis it is shown that even reverse osmosis membranes (the membranes with the smallest pore size) are not able to completely remove all pollutants. Combination of nanofiltration/reverse osmosis with other water treatment techniques (such as activated carbon filtration) is therefore necessary. This is no problem for the Dutch drinking water sector, since the principle of "multiple barrier treatment" is used in the Netherlands. For other countries, where the treatment plants are less advanced, the presence of pharmaceuticals and hormones may become a problem. Therefore, the policy towards pesticides, hormones and pharmaceuticals has to be changed, to prevent too many of these pollutants from entering the drinking water.