Dr. J. J. Marr has held positions in academic medicine and biochemistry; as Director of Divisions of Infectious Diseases; Vice Chairman, Department of Medicine; and Professor of Medicine, Biochemistry and Microbiology at Washington University, St. Louis University and the University of Colorado. Subsequently, he was Senior Vice Presidnt for Drug Discovery at Searle Pharmaceuticals, acted as a consultant to the National Institutes of Health and the World Health Organization, and now holds the position of Vice President for Research and Development/Chief Scientific Officer, Ribozyme Pharmaceuticals, Inc. Dr. M. Muller has held academic positions at the Medical University of Budapest, the Rockefeller University and the Carlsberg Laboratories in Copenhagen. He is a past President of the Society of Protozoologists, Founding Editor of Molecular and Biochemical Parasitology, and now heads the Rockefeller University Laboratory of Biochemical Parasitology. He has also acted as a consultant to the National Institutes of Health, the World Health Organization and to the Center for Disease Control.