The beneficial effects claimed for the use of garlic as a nutritional supplement include detoxification, antioxidation, antifungal activity, antibacterial activity, tumour suppression and, possibly, anti-ageing and rejuvenating effects. We have used the Hayflick system of cellular ageing in culture in order to test garlic for its anti-ageing effects on long-term growth characteristics, morphology and macromolecular synthesis of human skin fibroblasts. Our results show that an addition of garlic extract into the normal cell culture medium can support serial subculturing for over more than 55 population doublings in 475 days, and that this treatment has some youth-preserving, anti-ageing and beneficial effects on human fibroblasts in terms of maximum proliferative capacity and morphological characteristics. In comparison, similar or lesser doses of garlic extracts are growth inhibitory for cancerous cells that could not be grown over longer periods in the presence of garlic. To our knowledge, this is the first report of the effects of garlic on the long-term growth characteristics and macromolecular synthesis of normal human skin cells, the results of which have applications for both anti-ageing and anti-cancer research.