Vision: This investigation will contribute to the field of 'Sociology of Diagnosis' using autism as a case study. This nascent field focusses on the role that diagnosis plays in individual and professional understandings of health and illness. Sociologists consider diagnosis to have the following roles: i) A way of categorising people (as ill or healthy) ii) An intervention in itself with consequences for health iii) A social transactional process which clinicians, patient and carers m ay negotiate. Diagnosis may/may not be disclosed according to circumstance. While some patients seek diagnosis, others resist the use of diagnostic labels and argue diagnosis can be used as a form of social control. Building on previous work, I will explore adults' experiences of the utility and consequences of diagnostic categorisation using autism as a case study. Autism diagnosis is particularly relevant because the label is increasingly applied, the diagnosis has clear costs and benefits, and its application is frequently contested. Main method: An analysis of qualitative interview data, especially experiences of adults in the neurodiversity movement together with those of adults who have actively sought a clinical diagnosis of autism. The neurodiversity movement comprises politically mobilised adults with autism who frame neurological difference as a valuable aspect of human variation and argue against medical diagnosis claiming it pathologizes normal behaviour. Outputs : A series of five academic articles, a book and three short films exploring the themes of Diagnosis, Neurodiversity and Treatment.