Multi-institutional cooperative group trials require conformity to a uniform set of therapeutic guidelines so that all patients entered on the study are treated the same regardless of which participating center enters the case. This can come about only if an unambiguous, clearly defined treatment program is included in the protocol. Examples of confusing protocol guidelines from recent Group studies demonstrate how well-meaning participants can inadvertently deviate from study requirements. The Quality Assurance Review Center has developed an outline for the radiotherapy component of a study which has alleviated this problem considerably.