The use of unproven forms of therapy in cancer treatment is very common. In Brazil, the distribution by researchers to patients of an investigational agent called phophoethanolamine (PHOS) has led to a widely publicized scientific scandal. PHOS is a precursor to components of the cell membrane, with some published pre-clinical studies suggesting cytotoxic activity in cancer cells. The willingness of courts and of legislators to guarantee access to PHOS in spite of the lack of any clinical data and against the recommendations of scientific and medical organisations underscores the risks that unproven agents pose to regulatory authorities, health care systems and patients, and bears resemblance to other cases such as the controversy surrounding the approval of zidovudine for AIDS treatment by the FDA.