Received Oct. 10, 1998; revision received Jan. 20, 1999; accepted Jan. 26, 1999. From the Department of Psychiatry and Biobehavioral Sciences, the Neuropsychiatric Institute, the Alzheimer’s Disease Center, and the Center on Aging, University of California at Los Angeles; the VA Medical Center, West Los Angeles; the Department of Medicine and the Joseph and Kathleen Bryan Alzheimer’s Disease Research Center, Duke University Medical Center, Durham, N.C.; Glaxo Wellcome Research and Development, Research Triangle Park, N.C.; and the Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tenn. Address reprint requests to Dr. Small, Room 88-201, UCLA Neuropsychiatric Institute, 760 Westwood Plaza, Los Angeles, CA 90024-1759; firstname.lastname@example.org (e-mail). Supported by grants MH-52453, AG-13308, AG-10123, RR-00856, RG-96051, NS-31153, NS-26630, AG-05128, and AG-11268 from NIH; grant IIRG-94101 from the Alzheimer’s Association; grant 95-23330 from the California Department of Health Services; a VA postdoctoral fellowship; the Montgomery Street Foundation; and the Fran and Ray Stark Foundation Fund for Alzheimer’s Disease Research. The views expressed are those of the authors and do not necessarily represent those of the Department of Veterans Affairs.