The validity of information regarding drug toxicity in humans depends on the quality of the methods and instruments used to assess adverse drug events (ADEs). This study evaluates the quality of instruments used to assess and report ADEs to institutional review boards (IRBs) at US cancer centers. Forms from all 49 National Cancer Institute (NCI)-designated centers were assessed for utility in abstracting event type, severity, and causality; patient demographics; safety monitoring; and consequent changes in the conduct of the relevant study. Of the 55 items considered essential for ADE reporting, one item (event description) was present on all the forms. Seventy-eight percent of the instruments prompted for global introspection of the investigator, a method known to be unreliable. Of the 34 items that our panel of experts considered essential for event description, the median number of items present was four (domain = 1-11). The use of a validated tool to describe and assess event type, severity, and causality may lead to more timely, accurate identification of safety signals in cancer treatment.