The World Health Organization (WHO) is currently revising the ICD-10, which was approved in 1990, making the current period the longest in the history of the ICD without a major revision.  WHO is a global public health agency of the United Nations, whose constitutional responsibilities include the development and maintenance of international classification systems for health.  WHO’s Member States have agreed by international treaty to use the ICD as a basis for reporting health information that is usable and comparable across countries.
Within the context of the overall ICD revision process, the WHO Department of Mental Health and Substance Abuse has been assigned responsibility for managing the technical work of developing the chapter on mental and behavioral disorders. In developing the ICD-11 classification of mental and behavioral disorders, the Department has specified that substantial changes to existing mental disorder categories and definitions should be made through a transparent, international, multidisciplinary, and multilingual process that involves the direct participation of a broad range of stakeholders and is as free as possible from conflicts of interests. To assist the Department in all phases of the mental and behavioral disorders revision process, the WHO has appointed an International Advisory Group, chaired by Steven E. Hyman, which has in turn appointed a series of Working Groups in specific areas.  The Working Group on the Classification of Psychotic Disorders (WGPD), of which the first author is chair, has been charged with reviewing the evidence and developing proposals for schizophrenia spectrum and other primary psychotic disorders. The editorial is intended to provide an overview of the WGPD’s progress, and it follows a similar editorial on the classification of psychotic disorders in DSM-5. 
–Wolfgang Gaebel, Schizophrenia Bulletin