A survey of lumbar punctures performed in adults in a district general hospital over a two year period was carried out. As well as being used for conventional, specific indications, lumbar puncture was often employed as a screening investigation in undiagnosed neurological illness. Although this was not inappropriate in patients with meningeal symptoms and signs, or patients with disordered consciousness, lumbar puncture was also used in patients with focal neurological signs. Although the dangers of lumbar puncture in these latter patients, and the fact that it is unlikely to yield information unobtainable by other investigations have been stated by many authorities, almost 20% of patients fell into this group. This suggests that these points require further emphasis.