Flow injection dialysis (FID) offers good possibility for on-line sample pretreatment. Not only the analytes can be separated from matrix but also on-line dilution can be advantageous. Some ongoing developed systems using FID will be discussed as for the examples, determination of some anions (bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate) and cations (calcium, potassium, manganese and sodium) by ion chromatography; FID for flow injection spectrophotometric determination of ascorbic acid using permanganate solution. Features and advantages of the systems will be briefed.