Objectives: This is a pilot study with the objective of investigating general practitioner (GP) perceptions and experiences in the referral of mentally ill and behaviourally disturbed children and adolescents. Design: Quantitative analyses on patient databases were used to ascertain the source of referrals into Child and Adolescent Mental Health Services (CAMHS) and identify the relative contribution from GP practices. Qualitative semistructured interviews were then used to explore challenges faced by GPs in referring to CAMHS. Setting: GPs were chosen from the five localities that deliver CAMHS within the local Trust (Peterborough City, Fenland, Huntingdon, Cambridge City and South Cambridgeshire). Participants: For the quantitative portion, data involving 19 466 separate referrals were used. Seven GPs took part in the qualitative interviews. Results: The likelihood of a referral from GPs being rejected by CAMHS was over three times higher compared to all other referral sources combined within the Cambridge and Peterborough NHS Foundation Trust. Interviews showed that detecting the signs and symptoms of mental illness in young people is a challenge for GPs. Communication with referral agencies varies and depends on individual relationships. GPs determine whether to refer on a mixture of the presenting conditions and their perceived likelihood of acceptance by CAMHS; the criteria for the latter were poorly understood by the interviewed GPs. Conclusions: There are longstanding structural weaknesses in the services for children and young people in general, reflected in poor multiagency cooperation at the primary care level. GP-friendly guidelines and standards are required that will aid in decision-making and help with understanding the referrals process. We look to managers of both commissioning and providing organisations, as well as future research, to drive forward the development of tools, protocols, and health service structures to help aid the recognition and treatment of mental illness in young people.