DC-LD is a new classification system providing operationalised diagnostic criteria for psychiatric disorders, intended for use with adults with moderate to profound learning disabilities. It may also be used in conjunction with the ICD-10 and DSM-IV manuals in a complementary way, when working with adults with mild learning disabilities. DC-LD was developed by a working party convened on behalf of the Faculty for the Psychiatry of Learning Disability of the Royal College of Psychiatrists and the Penrose Society. The work was further informed by a wider consultation group and a piloting exercise. It is only suitable for use by professionals trained in psychiatric diagnosis. The use of DC-LD will hopefully enhance clinical practice and facilitate future research in this area.