The impact of enhanced coagulation on the formation of trihalomethanes (THMs) from drinking water was studied in four treatment plants in Nicaragua. Enhanced and conventional coagulation techniques were compared with regard to the removal of natural organic matter (NOM), which was measured by surrogate parameters. The enhanced coagulation process showed a better removal of NOM, and as a consequence the THM formation was up to 50% lower than with conventional coagulation. The influences of chlorine dosage, temperature, pH and contact time on the THM formation in water treated by enhanced and conventional coagulation were also studied.