Introduction In the last decade it has been proposed that individuals who are at an elevated future risk of developing psychosis compared to the general population can be identified using operationalised criteria. Those who fulfil these criteria are labelled as having an At-Risk Mental State (ARMS) for psychosis. Research in working-age adults has reported a lowering of the short-term rate of transition of such individuals to psychosis over successive cohorts. Nevertheless, such individuals report poor psychosocial functioning and high distress levels. To date, there has been a dearth of research specifically focussed on the concept of the ARMS in adolescents. Thus it is not established how these young people present to mental health services, what mental health diagnostic categories, if any, they would fulfil and what their short-term outcomes are in terms of mental health and psychosocial functioning. Moreover, it is unknown how this group may experience the label of being ‘at-risk’ and whether these individuals would benefit from the ARMS criteria being made an official diagnostic category. The aim of this study was to investigate how young people fulfilling the ARMS criteria present to services, to characterise them and report the short-term outcomes, in terms of mental health and functioning. The views and experiences of young people with the ARMS label and mental health professionals potentially working with this client group were also explored. Methods Two separate projects were completed: Project 1; The Follow-up of the At-Risk Mental State (FARMS) project and Project 2; The Professional Attitudes towards the At-Risk Mental State (PAARMS) project. Study 1 of the FARMS project involved a prospective longitudinal cohort study and investigated how adolescents categorised as having an ARMS initially present to mental health services and fared over a six month follow-up period. Study 2 involved recruiting a purposive sample of participants fulfilling the ARMS criteria from Study 1, into a qualitative study. An Interpretative Phenomenological Analysis (IPA) framework was then used to explore the personal understanding and experiences of these young people in relation to the ARMS concept. The PAARMS project used a mixed methods approach in order to evaluate the attitudes and experience of Child and Adolescent Mental Health Service (CAMHS) professionals in relation to the ARMS concept. Firstly, in-depth interviews were conducted with a purposive sample of six CAMHS clinicians who work in Early Intervention in Psychosis (EIP) services regarding their experience and attitudes in relation to working with young mental health service-users who have the ARMS label. Secondly, a survey involving 180 CAMHS clinicians was conducted. Results Study 1 of the FARMS project confirmed that adolescents fulfilling the ARMS criteria present to services with significant levels of reported psychopathology and functional impairment. Auditory perceptual disturbance was the most frequently reported ‘positive’ symptom whilst 70% of participants met the threshold for at least one current ICD-10 Axis I psychiatric diagnosis. In terms of short term outcomes, transition rates to psychosis were low (1/29; 3%) with a handful of individuals (7/29; 24%) demonstrating significant remission of symptoms and/or significant improvements in psychosocial functioning. The findings from Study 2 indicate that young people wish to be told about their condition upon identification and do not report experiencing significantly negative or distressing instances of stigma, though this was a voiced initial concern. Talking to mental health professionals and possibly peers, who also experience similar symptoms, are perceived as the most beneficial elements of support offered by services. Finally, CAMHS professionals participating in the PAARMS project reported being reluctant to recommend medication as a first-line treatment strategy. However, monitoring, psycho-education and psychological therapies were widely endorsed. Identification and management of adolescents with the ARMS label was viewed as challenging and complicated by a variety of factors including maturational process and a lack of official guidelines and protocols. Discussion The results of this study not only characterise how adolescents fulfilling the ARMS criteria present to services but also inform future debates regarding the ARMS concept as a distinct diagnosis. These findings should therefore facilitate the development of new policies for the identification and management of the condition in young people and address areas of clinical practice that require immediate attention. Future research is required to establish whether these initial findings are generalisable to services elsewhere and to evaluate plausible interventional approaches that target distressing symptoms and functioning.