: The WHO International Classification of Diseases is used in many national applications to plan, manage and fund through case mix health care systems and allows international comparisons of the performance of these systems. There is no such measuring tool for health interventions or procedures. To fulfil this requirement the WHO-FIC Network recommended in 2006 to develop an International Classification of Health Interventions (ICHI). This initiative is aimed to harmonise the existing national classifications and to provide a basic system for the countries which have not developed their own classification systems. It is based on the CEN/ISO ontology framework standard named Categorial Structure defined from a non formal bottom up ontology approach. The process of populating the framework is ongoing to start from a common model structure encompassing the ICD 9CM Volume 3 granularity.