An ion chromatographic method was developed for the determination of triazine herbicides in environmental samples. Considering the polar nature of triazines, a cation-exchange column with a multi-mode pellicular packing was used. Optimization of the eluent (organic modifier concentration and ionic strength) is described with reference to the separation, on-line clean-up and preconcentration procedure. Several enrichment materials were evaluated and detection limits below 100 ng/l were achieved with a reversed-phase silica. The determination of triazines in tap water and river water samples was performed with UV detection (220 or 263 mm).