The drainage routes from the subarachnoid space to the nasal mucosa were investigated in autopsy material. Indian ink, applied post–mortem to the olfactory groove, promptly filled the perineurial spaces around the olfactory nerve branches in the dura, the lamina cribrosa and the submucosal tissue in the nose. In a case of recent subarachnoid haemorrhage, the perineurial spaces even around the most distal olfactory nerve branches were congested with blood and there was an abundant accumulation of red corpuscles in the apical part of the nasal mucosa. Iron–containing pigment was found in the perineurial spaces of proximal and distal olfactory nerve branches as well as in the nasal mucosal stroma in cases with older haemorrhagic lesions. The findings show that the perineurial spaces provide an efficient drainage route from the subarachnoid space to the nasal mucosa in cases with haemorrhagic cerebral lesions. A complementary drainage route for the cerebrospinal fluid was indicated by the presence of indian ink, red corpuscles and iron pigment in arachnoid villi, which penetrated the lamina cribrosa and ended in the nasal submucosal tissue. Iron in the deep cervical lymph nodes should not be taken as evidence of transport from the CNS, since iron pigment was also found in cases without intracranial haemorrhage.