The development and psychometric evaluation of the CANDID is reported. It was developed by modification of the Camberwell Assessment of Need (CAN). The four principles that informed the development of the CAN and the CANDID are 1. people with intellectual disabilities and mental health problems have basic needs like everybody else along with specific needs associated with their conditions 2. the primary aim is to identify rather than describe in detail each need; once a need is identified more specialist assessment can be conducted in those domains 3. needs assessment should be possible to be conducted by a wide range of people, so that it can be applied in routine clinical practice 4. there may be differences of opinion about the existence of need amongst people involved and therefore different points of view should be recorded separately. The reliability and validity of CAN have been investigated and found to be acceptable. Research studies using CANDID are summarised here.