A lumbar puncture may be performed for various reasons, but is commonly used to facilitate the diagnosis of central nervous system infections in infants and children. It involves inserting a needle into the lower spine to obtain cerebrospinal fluid, which is then sent for testing in a laboratory. The results of the tests, together with a clinical assessment of a patient, can guide the effective treatment of infections and reduce the risk of neurological conditions. This article outlines some of the reasons why lumbar punctures are performed, discusses the practical aspects of the procedure and explains how nurses can effectively support the child and their family, while also assisting the practitioner undertaking the procedure.