Unlike physical sensors, which are mass-produced using planar electrochemical technology and silicon micromachining, the manufacture of biosensors (chemical transducers based on a biologically selective and sensitive element) is currently limited to screen-printed glucose sensors. The purpose of this text is to provide electronics engineers, chemists, materials scientists and biotechnology researchers with an interdisciplinary review of electrochemical theory and microelectronic fabrication techniques and their combination to produce cheap compact biosensors for on-the-spot (and even "in vivo") measurements. Chapters 1 and 2 introduce microelectrochemical sensor applications and basic electrochemical principles. Chapters 3 and 4 compare potentiometric, voltammetric and conductometric measurement techniques and detail microelectronic fabrication processes for planar silicon-based IC voltammetric sensors and an alternative thick-film process. Chapter 5 evaluates the processing and packaging of CMOS-compatible biosensors.