Sulphides in water samples were determined by stripping chronopotentiometry in a computer controlled flow system with a flow-through electrochemical cell. The working electrode was a porous glassy carbon electrode coated with Nafion and mercury. The sample was diluted with 0.1 mol L(-1) NaOH and analysed. Sulphides in the sample were collected in the porous electrode as mercury sulphide and then stripped by a current of -500 microA. The limit of detection was found to be 1.6 microg L(-1) and 0.5 microg L(-1) for 1 mL and 5 mL of preconcentrated sample, respectively. The linear range for 1mL sample was found to be 5-400 microg L(-1). The repeatability and reproducibility was found to be 2.6% and 4.8%, respectively. The method was applied to analyses of waste water samples from a tannery.