The chlormation process is one of the water treatment plant used for the disinfection of water. The disinfection by products are trihalomethanes such as chloroform, bromodichloromethane, dibromochloromethane and bromoform. Headspace Solid-Phase Microextraction (HS-SPME) and Direct Solid-Phase Microextraction (DI-SPME) (100 urn polydimethylsiloxane fiber) were studied for analysis of trihalomethanes in water samples. The effect of stirring rate, extraction time, extraction temperature and desorptiontime on the analysis were investigated. The linearity, detection limit and repeatability were evaluated by using the optimized HS-SPME and DI-SPME techniques. The percentage recoveries by spiking samples with standard solutions of THMs were also examined and compared with the conventional liquid-liquid extraction. The percentage recoveries of HS-SPME and DI-SPME techniques showed no significant difference by using t-test (95% probability). The results can be concluded that HS-SPME technique has a great potential for determination of trihalomethanes with lower limit of detection. © Medwell Journals, 2009.