Introduction: This study aims to explore the ways in which Asperger’s Syndrome and High Functioning Autism are understood by those who have received a diagnosis in adulthood. The experience and understanding of diagnosis in adulthood has been little researched with only a small number of qualitative studies having been completed (Cousins, 2001; Molloy & Vasil, 2004; Punshon, 2006). These studies all highlight the importance of the beliefs held about Asperger’s Syndrome on the experience of diagnosis and post-diagnostic identity development. Due to the increasing awareness and diagnosis of Asperger’s Syndrome in adulthood, research into how the diagnosis is understood is invaluable for clinicians supporting individuals through the process. Method: This study uses a Q-methodology (Stephenson, 1953) to build upon recent qualitative research. The methodology is based on two techniques, the Q-sorting process and Q-factor analysis. For the Q-sorting process a set of 52 statements were developed which attempted to provide coverage of the understanding of Asperger’s Syndrome currently in the public domain. A wide range of sources were used to develop the Q-set, including a focus group with six adults with Asperger’s Syndrome. Eighteen individuals who had received their diagnosis in adulthood were recruited to complete the Q-sorting process, which involved them having to rank the statements based upon their agreement with them. Additionally a semi-structured interview was completed to gather information regarding the sort and supplementary demographic information. Results: Q-factor analysis involving principal components analysis and varimax rotation was then carried out. This led to four statistically significant and theoretically meaningful factors being extracted. The four factors were interpreted using the additional information gathered, and were labelled ‘An important part of me’, ‘It is a lifelong disability’, ‘Confused about myself, and ‘Support can bring improvement’. Discussion: The findings were discussed with consideration of the clinical implications and scope for further research. Particular emphasis was placed on discussing three main areas ‘acceptance and adjustment’, ‘consequences of diagnosis’ and ‘theoretical conceptualisations’. The importance of further research into the links between understanding and mental health were highlighted.