Headache is the commonest complication of spinal puncture. There is no significant difference in the incidence of headache after lumbar puncture, whether or not the puncture is followed by injection of an anesthetic agent. The sequence of events leading to postlumbar puncture headaches is probably (1) decreased volume of cerebrospinal fluid with lowered pressure; (2) increased differential between the pressure of the cerebrospinal fluid and the intracranial venous pressure; (3) dilation of venous structures with increase in brain volume; and (4) production of tension on the pain sensitive areas in the cranium. Prevention of postlumbar puncture headache consists largely in attempts to avoid the development of the pressure differential between that of the cerebrospinal fluid and intracranial venous pressure. Treatment consists of analgesics, hydration and attempts to restore normal cerebrospinal fluid pressure.