We have selected a group of young patients, without any pathological past, admitted in the hospital after traffic accidents. CSF was examined at various periods after the accident as well on the cytological as on the biological point. If the lumbar punction is undertaken in the very few hours after the trauma or at the time of the onset of a meningeal syndrom, the presence of oxyhemoglobin may confirm the abnormal bleeding and makes difference with the stitching of a vessel during the punction. The presence of macrophages red blood cell containing may characterize a 2--3 days bleeding. The presence of macrophages containing iron pigment may confirm that the bleeding appeared at least 6--7 days before the cytological patterns and the chromoprotein assays provide a valuable help to the physiologist and may be applied to all types of meningeal hemorrhages.