This paper presents a functional architecture, system level design, and electronic evaluation of a unilateral vestibular prosthesis. The sensing unit of the prosthesis is a custom-designed one-axis microelectromechanical system (MEMS) gyroscope. Similar to the natural semicircular canal, the MEMS gyroscope senses angular motion of the head and generates voltages proportional to the corresponding angular acceleration. The voltage is then converted into electric current pulses according to the physiological data relating angular acceleration to the spike count in the vestibular nerve. The current pulses can be delivered to stimulate the corresponding vestibular nerve branch. Electronic properties of the vestibular prosthesis prototype have been systematically evaluated and found to meet the design specifications. A unique feature of the present vestibular implant prototype is the scalability: the sensing unit, pulse generator, and the current source can be potentially implemented on a single chip using integrated MEMS technology.