Depression is common in Huntington's disease, but standard rating scales have doubtful validity in this population. Using data from the European Huntington's Disease REGISTRY study, the authors examined the discriminant value of items on the Beck Depression Inventory (N=843) and the Hamilton Rating Scale for Depression (N=768). Good discriminators of depression, apart from "depressed mood," were "guilt," "loss of interest," and "suicidality." Items that discriminated poorly were "weight loss," "sleep disturbance," "loss of appetite," "psychomotor retardation," "agitation," and "irritability." These findings highlight the limited usefulness of these scales within the area of Huntington's disease.