People with mental health illness, particularly those affected in the long-term, experience higher rates of morbidity and mortality than the general population. It is, therefore, crucial to meet their physical health needs as part of delivering a high quality service. This article reports on how nurses in a medium secure mental health unit used the 'plan, do, study, act' approach (Deming 1986) as a practice improvement tool to introduce a system of monitoring the physical health of service users.