In this study of 300 neurological inpatients aged between 18 and 60 years the incidence of post-lumbar-puncture headache (PPH) was 37.3%. The more severe the headache, the more frequently it was associated with dizziness, nausea, vomiting, and tinnitus. If PPH occurred during the first day after lumbar puncture (LP), it was more severe, and lasted longer than PPH, which started later. The incidence of PPH and associated symptoms decreased with increasing age, and was much higher in females than males. The sex difference was nearly exclusively explained by a marked preponderance of PPH in females below 40 years of age, i.e. women in the fertile age. Furthermore, there was a decreased incidence of PPH and associated symptoms in patients with an initial higher than average cerebrospinal fluid (CSF) pressure (162 mm H2O). All these differences were statistically significant. Particularly high frequencies of PPH were found in young women with an initial CSF pressure lower than mean.