Electrochemical sensors are widely used either directly or as an integral part of a device for biological, environmental and other monitoring. Microelectronic fabrication technology can be used to make highly reproducible, small scale, geometrically well-defined structures in arrays of identical or different sensors. These technologies include thick and thin film deposition, photolithographic pattern definition and chemical and plasma etching. Thus, multiple or redundant sensors can be constructed on a single, relatively small substrate. Because of the advantages in the structure and size of electrochemical sensors produced by these fabrication techniques, new or classical sensing approaches can be exploited for the development of novel sensors. Miniature high temperature and ambient temperature electrochemical sensors will be used as examples to illustrate this approach to sensor development.