A selective and sensitive ion chromatographic method has been developed for the determination of beryllium in a number of water samples at low-microg/l concentrations. The separation was performed on a 250x4.0 mm I.D. iminodiacetic acid functionalised silica gel column. Chromatographed Be(II) was detected using visible detection at 590 nm following post-column reaction with chrome azurol S (CAS). The optimum separation and derivatisation conditions were studied in detail. The optimum eluent conditions were found to be 0.4 M KNO3, adjusted to pH 2.5 using HNO3, with optimum post-column detection being achieved using a solution containing 0.26 mM CAS, 2% Triton X-100, 50 mM 2-(N-morpholino)ethanesulfonic acid, pH 6.0. Under the above conditions, the concentration detection limit for Be(II) was found to be 3 microg/l in a standard solution and 4 microg/l in a typical tap water sample, using a 250 microl injection. The method was linear over the investigated range of 10 microg/l to 10 mg/l and highly reproducible. The method was successfully applied to a number of water samples of varying matrix complexity, including simulated seawater, and also to a natural freshwater certified reference material NIST 1640.