Arsenic poisoning, a disease of the past, was recently found in 74 patients in Singapore over a 15-month period. Most victims (70%) had a chronic form of poisoning and 64% of the cases were caused by a local anti-asthmatic herbal preparation containing 12,000 ppm of inorganic arsenic sulphide. The other patients were poisoned by six other brands of herbal preparations used for the treatment of asthma and a variety of other illnesses. Subsequent investigations revealed another 22 other brands of Chinese herbal preparations containing high concentrations of inorganic arsenic ranging from 25 to 107,000 ppm, of which most were imported. Nearly 40% of the patients had taken the medicine for less than six months, but the others had a longer history of exposure ranging from one to 15 years. Systemic involvement was confined mainly to the skin (91%), nervous system (51%), gastrointestinal system (23%) and blood (23%). Malignancy of the skin was present in six patients, and of the visceral samples, toxicological confirmation was found in half of the cases investigated. There was no correlation between the clinical status of the patients and their tissue arsenic content. The importance of arsenic poisoning by herbal preparations is discussed, as there are no known reports of their association.