The Health of the Nation Outcome Scales (HoNOS) were developed to provide a single index in order to enable the government target 'to improve significantly the health and social functioning of mentally ill people' to be quantified. They were intended to be applicable to all adults (including older people), across a wide range of settings so that services in different localities could be compared and changes both within individuals and within services could be measured. In 1999 the HoNOS65+ was launched with a modified glossary for older people. The HoNOS has been formally adopted as the preferred outcome measure for adults of working age. There has been no such formal adoption of the HoNOS65+, or any other outcome measure, for mental health services for older people. This review summarises how the HoNOS was originally developed and validated. Studies with older people, which have used both the original definitions and those developed for the HoNOS65+ are reviewed focusing on data on the reliability and validity of the HoNOS and HoNOS65+ with older people. Finally the question of whether the HoNOS or HoNOS65+ is suitable as an outcome measure in routine clinical practice in services for older people is addressed.