1. From the Departments of Psychiatry (D.R.L.), Biostatistics, University of Iowa, Iowa City; CHDI Management/CHDI Foundation (S.S.S., C.S.), Princeton, NJ; Macquarie Medical School (C.L.), Macquarie University; and Department of Neurology (Huntington disease Service) (E.A.M.), Westmead Hospital, University of Sydney, Australia.