A biotechnology resource center to enhance biomedical research use of electron spin resonance spectroscopy has been established in Milwaukee, Wisconsin, at the Medical College of Wisconsin and is associated with the Milwaukee County Medical Complex. The equipment of the Center includes five major instruments: ENDOR, ELDOR, Pulse ESR, and two conventional ESR spectrometers with capacities to operate at three microwave frequencies over a broad range of temperatures. The missions of the Center are: (1) to provide advanced instrumentation and expert technological and scientific support that can be utilized by visiting scientists in the biomedical field on a collaborative basis; (2) to utilize the equipment in an extensive program of Core Research, particularly focusing on analysis of clinically obtained samples, both from the point-of-view of contributing to fundamental knowledge and also of developing diagnostic methods; (3) to develop new types of ESR apparatus that are not commercially available, often on the basis of needs that arise in the course of collaborative or core research; and (4) to act as an educational resource offering formal short courses at several levels of sophistication and providing on-site practical experience with conventional and advanced spectrometers. A central thrust of this Center is development and application of methods to study motion, particularly in the range of 10 to the minus 3rd power to 10 to the minus 6th power sec., a time range not readily accessible by other physicochemical methods. The Center is an international, national, and regional resource probably the most extensive biomedically oriented ESR Center in the world.