A case of acute thallium poisoning in a 67-year-old Chinese woman is described. She presented with acute pain in the chest, abdomen, and lower limbs. The diagnosis was not made, however, until alopecia developed. Detoxification treatment, which included Prussian blue (potassium ferric hexacyanoferrate) was then given, but further neurological damage occurred. The patient's motor function recovered after 1 year, but residual sensory neuropathy remained. This case illustrates that tissue-bound thallium may cause prolonged neurological damage if detoxification therapy is not commenced within 72 hours of the onset of acute poisoning. Acute abdominal pain and painful neuropathy in the lower extremities are important early diagnostic clues for timely therapy. However, by the time alopecia develops--typically around 2 weeks after the onset of symptoms--detoxification therapy may not be able to prevent the development of prolonged neurological damage.