The rise and fall of the ten-day rule.

The introduction of the 10-day rule is described together with the difficulties arising from its application. The reasons for believing it is now unnecessary are summarised. The new recommendations from the National Radiological Protection Board stress the importance of identifying a pregnancy after a period has been missed and provide advice regarding the radiography of the patients. The rationale of these suggestions is given. The importance is stressed of keeping both male and female gonad doses to a minimum during the reproductive years.