Pharmacological treatment with polyanions or amphotericin B in hamsters with experimental scrapie reveals that it is possible to delay the appearance of the disease only when the drug is given before the invasion of the agent into the clinical target areas of the brain. We suggest such early treatment may be possible for individuals at high risk of acquiring the disease, such as healthy mutation-positive relatives of patients with familial Creutzfeldt-Jakob disease or Gerstmann-Sträussler syndrome, or recipients of potentially contaminated pituitary-extracted human growth hormone.