Sleeping sickness, or African trypanosomiasis in man, caused by 5. brucei gambiense or T. brucei rhodesiense, runs a complex course leading, if untreated, to the late-, or secondary-stage, and death. T. b. gambiense produces initially mild symptoms and a chronic infection which may last for years but T. b. rhodesiense infections are generally acute, with severe deterioration and death within a few weeks or months. The later stage is associated with the parasite becoming established within the brain, after which successful chemotherapy necessitates the use of drugs that will cross the bloodbrain barrier, otherwise t-elapses will occur. Since the 1940s such treatment has been limited to the toxic organic arsenicals (eg. Melarsoprol) which can themselves cause serious side-effects. Melarsoprol causes fatal reactive encephalopathy in up to IO% of treated patients ‘. 2. Recent finding s suggest that difluoromethylornithine(DFMO), an inhibitor of ornithine decarboxylase, offers a hopeful alternative.