Age-related changes in liver function are important because they may promote susceptibility to adverse drug reactions, neurotoxicity, atherosclerosis, and other important diseases in older people. Age-related changes in the rat hepatic sinusoidal endothelium, termed pseudocapillarization, have been described recently and these may contribute to hepatic impairment. The present study has examined surgical and post-mortem specimens with immunohistochemistry and transmission electron microscopy to determine whether pseudocapillarization also occurs in older humans. The age of the subject, independent of systemic disease or hepatic pathology in surgical and post-mortem samples of human liver, was associated with increased peri-sinusoidal expression of von Willebrand’s factor, collagen I, collagen IV, and staining with Masson’s trichrome. Electron microscopy revealed significant age-related thickening of the sinusoidal endothelium (young 165±17 nm, middle age 222±11 nm, older 289±9 nm, p< 0. 001) with loss of fenestrations (young 7. 7±0. 7 per 10 µm, middle age 3. 6±0. 5 per 10 µm, older 1. 5±0. 4 per 10 µm, p< 0. 001), and agerelated deposition of basal lamina and collagen. In conclusion, ageing in humans is associated with morphological changes in the sinusoidal endothelium and space of Disse which are presumptively related to the ageing process and potentially represent an important link between the ageing process and disease susceptibility. Copyright© 2003 John Wiley & Sons, Ltd.