The ICD is being revised for its 11th revision, and empirical efforts are being made to assess the use of the ICD-10 and how it can be improved.

Our aim was to investigate the use of the ICD-10 in Japan, which is to be presented in comparison to its use at a global level.

1) We investigated the frequency of use and the perceived importance of every diagnostic category in the ICD-10. 2) We asked about more specific issues that were being debated at that time, e.g. incorporation of disability component, approaches to the high rate of NOS and co-morbidity.

1) 80 university-based hospitals and 147 councilors of the Japanese Society for Psychiatric Diagnosis (JSPD) were contacted for participation, of which 49 (61%) and 53 (36%) responded respectively. 2) 452 members of the JSPD and 80 chief professors from every department of psychiatry were contacted and 245 individuals in total responded (46%).

1) “Unspecified” and “other” items were generally neither used frequently nor considered as important. Other trends pertaining to more specific diagnostic categories were also observed. 2) Overall psychiatrists in Japan appeared to be conservative about radical changes, and they tended to accept NOS and co-morbidity cases as a necessary condition for operational diagnosis instead of a flaw of the classification system itself.

The results presented here come from Japan only, but they can be informative in further investigating issues related to diagnosis and classification elsewhere as well as globally.