A modular electrochemical microanalysis system (ELMAS) has been developed at the Karlsruhe Research Center within the project "Microsystem Technology". This self-calibrating system contains ISFET-microsensors and gas pumping micro membrane pumps; The transport of liquids is realized by changing the air pressure on the liquid in the storage reservoir. The pH-ISFETs show a fast response and with flow rates of 200-300 mu l/min, a cycle time for calibration and sensor measurement of 60 s can be achieved. With increasing flow rates, the cycle time can be decreased but the liquid consumption rises because of dispersion. Approximately 50 mu l of analyte and a maximum of 70 mu l calibration liquid is required for one cycle. Because of the gas buffer in the storage reservoir the fluid flow is delayed by 5 s compared to the control signals of the micropump.