Report 92 makes recommendations on how often routine checks should be made in Radiotherapy.   The areas covered include quality control of linear accelerators, use of portal imaging, in-vivo dosimetry and checking treatment plans.  In each case, the balance is quantified between the resources required for the checks and the potential detriment in performing checks too infrequently or not at all.  Enough information is given for readers to construct cases for their own particular circumstances, and the scope and limitations of the methodolgy are explained clearly enough that the method may be applied to new technologies and processes as they are brought into clinical use.  The Report will be of interest to radiotherapy physicists, clinical oncologists and therapy radiographers.