The prevention, detection and amelioration of adverse events feature prominently in oncology protocols, the detailed plans for conducting clinical trials of therapies for the treatment of cancer. This paper summarises a safety review of such protocols prior to implementing OaSiS, a decision support system (DSS) in oncology . Oa- SiS, shortly to undergo preliminary field evaluation in an oncology clinic, has been strongly influenced by the ONCOCIN , OPAL  and EON  family of computer systems developed at Stanford University in the last fourteen years. Like EON, OaSiS is a shell to be used with any oncology protocol provided it can be suitably represented. It does not support or critique the design of new protocols as do OPAL and DaT . Even so, the safety review is still relevant to design tools like OPAL and DaT.