Haloacetic acids (HAAs) are by-products from disinfection process in water treatment plant by the interaction of chlorine or other disinfectants with naturally occurring organic and inorganic matters in water. It has been causing concern due to potential harmful effect from long-term exposure. Separation of nine HAAs in water samples was developed by suppressed ion chromatography. The conditions were performed by using IonPac AS11HC (2×250 mm) ion exchange column, Potassium hydroxide (KOH) as the eluent with the gradient system and conductivity detector. All of analytes could be separated from fluoride, nitrate, chloride and sulfate ion, which commonly anions occur in drinking water, by using the two optimized gradient systems. The linearity of MCAA, DCAA, TCAA, MBAA, DBAA, TBAA, BCAA, BDCAA and DBCAA were 7-1000, 5-1000, 5-1000, 7-1000, 10-1000, 300-1200, 5-1000, 10-1000 and 200-1000 μg L^-1, respectively, with the correlation coefficient in the range of 0.9871-0.9991. The detection limits were 7, 5, 5, 7, 10, 200, 5, 10 and 170 μg L^-1, respectively. The repeatabilities of the peak area (%RSD, n = 5) were found in the range of 0.90-4.57% and the reproducibility in the range of 1.35-7.62%RSD. © 2010 Asian Network for Scientific Information.