The move in the United Kingdom (UK) from institutional to community care has led to an inevitable increase in the involvement of practice nurses (PNs) in mental health care. Around 20 000 PNs are currently working in the United Kingdom (UK). However, the extent and nature of PN involvement in delivering mental health interventions has not been adequately explored.This study aimed to quantify practice nurses' involvement in delivering mental health interventions in primary care settings.A questionnaire was sent to a random sample of 1500 practice nurses registered with the Practice Nurse Forum at the Royal College of Nursing. Sixty per cent of questionnaires were returned; however, once non-eligible respondents were removed an adjusted response rate of 54% was achieved.Practice nurses play a significant role in the assessment and treatment of mental health problems, most frequently via the administration of depot antipsychotics and the screening for depression. However, antipsychotic side-effects were infrequently monitored and PNs' understanding of treatment issues in depression is poor. These findings may be associated with the reported lack of mental health training that PNs have received.The findings of this study have important implications for the training of practice nurses in mental health, specifically in the areas of medication management and the detection of mental disorders.