A sensitive method has been developed for ion chromatographic determination of sulfide, sulfite, thiosulfate and thiocyanate in their mixtures. Sulfide, sulfite, thiosulfate and thiocyanate were eluted at retention times of 5.1, 8.8, 15.0 and 21.5 min, respectively, from an ion-exchange column with a 6·10 − 3 M carbonate eluent containing 15% (v/v) acetonitrile at a flow-rate of 0.5 ml min − 1. The sulfur anions in the effluent from the column were monitored by photometric measurement of the excess of iodine (triiodide) for a postcolumn iodine–azide reaction catalyzed by each of sulfide, thiosulfate and thiocyanate and for a postcolumn reaction of iodine with sulfite. Therefore, chromatograms obtained for the sulfur anions gave negative peaks, based on the decrease in the absorbance from background. The optimal conditions for the catalytic postcolumn reaction in the presence of the sulfur anions, with the exception of sulfite, were established by varying concentrations of iodine, iodide, acetic acid and azide in the postcolumn-reaction mixture, reaction temperature and length of the reaction tube. Calibration graphs, plotted as peak heights vs. concentrations, were linear up to 5.00·10 − 7 M for sulfide, 4.50·10 − 6 M for sulfite, 5.00·10 − 7 M for thiosulfate and 2.00·10 − 7 M for thiocyanate respectively. Detection limits at S/ N=3 were 0.14 ng for sulfide, 2.40 ng for sulfite, 0.16 ng for thiosulfate and 0.05 ng for thiocyanate. The proposed method was successfully applied to the determination of sulfide, sulfite and thiosulfate in hot-spring water samples.