The impact of ageing on the choroid plexus (CP)‐CSF circulatory system has largely been un‐investigated, or has been of interest only in relation to neurological disease. This paper reviews the evidence for age‐related changes to the CP‐CSF system and compares changes with disease states where appropriate. The changes discussed include reduced ion transport capabilities, evidence for oxidative stress, altered hormone interactions, decreased CSF secretion rates in animal models and the contradictory nature of human data, reduced clearance of protein from CSF, and slower fluid turnover. The potential impacts of these changes are highlighted, including the possibility of reduced resistance to stress insults and slow clearance of toxic compounds from CSF with specific reference to amyloid peptide. Other impacts may include the reduced ability of CSF to act as a circulating medium for hormone and growth factors to reach their brain targets, and reduced homeostasis of CSF nutrients (amino acids, vitamins), which might influence brain interstitial fluid homeostasis. Microsc. Res. Tech. 52:31–37, 2001. © 2001 Wiley‐Liss, Inc.