Michael J. Sanfelippo, recently retired as Technical Director of Coagulation Services at Marshfield Laboratories, Marshfield, Wisconsin. He holds a Master of Science degree from Marquette University in Clinical Pathology with a major in Hematology. He has published numerous articles in the medical literature. In addition, he has served as a technical consultant to several of the companies that make reagents and instruments for coagulation testing. He was formerly on the faculty of the University of Wisconsin - Milwaukee and the Milwaukee School of Engineering.