An apparently complex situation has been caused in recent years by the
definition of a number of new quantities in radiation protection. The
complexity is reduced if it is recognised that each quantity is suita
ble for one of three roles; risk estimation, operational measurement o
r primary standardisation. This understanding leads to an appreciation
of the required inter-relationships between the values of the quantit
ies. The recently introduced quantities, their roles, and the requirem
ents of their inter-relationships are discussed.