Aims and methodTo assess junior doctors' knowledge of the procedures involved in involuntary admission of patients detained under Sections 5(2), 2 and 3 of the Mental Health Act 1983. A semi-quantitative research study of junior trainees affiliated to two psychiatry training schemes was carried out.ResultsTrainees' knowledge of professionally relevant sections of the Mental Health Act was patchy. Knowledge correlated significantly with experience in clinical practice and with experience of using mental health legislation. Surprisingly, in-service training in mental health legislation had no effect on participants' knowledge.Clinical implicationsLack of knowledge and understanding raises the possibility of inappropriate use of the mental health legislation. This threatens patients' fundamental rights and can lead to complaints or litigation. There is a clear need to address this at an early stage in psychiatry training.