Because of concerns over the health effects of disinfection by-products (DBPs), the removal of DBPs precursors from the Terkos Lake water (TLW) of the Istanbul City by enhanced coagulation and powdered activated carbon (PAC) adsorption was investigated. The results of this study clearly indicated that the effects of coagulation and PAC adsorption on the removal of dissolved organic carbon (DOC) and DBPs precursors from TLW were complementary. Maximum DOC removal efficiency of enhanced coagulation by ferric chloride was 45%, and this type of natural organic matter (NOM) is preferentially large organic molecules with negatively charged functional groups. However, supplementing enhanced coagulation with PAC adsorption increased the removal of DOC to 76%, and PAC adsorption removed mostly low molecular weight and uncharged NOM substances. This study shows that the combination of enhanced coagulation and PAC adsorption can be more effective than enhanced coagulation alone for meeting the Turkish trihalomethanes (THM) limit of 150 mu g/L.