1. Division of Clinical Pharmacology, Department of Medicine, Johns Hopkins University, Baltimore, Maryland 21287.
2. Roche Laboratories Inc., Nutley, New Jersey 07110.
3. University of Pennsylvania, Philadelphia, Pennsylvania 19104.
4. University of North Carolina, Chapel Hill, North Carolina 27514.
5. Harvard School of Public Health, Boston, Massachusetts 02115.
6. National Institute of Allergy and Infectious Diseases, Rockville, Maryland 20892.