Whereas modern dietary advice emphasizes the importance of freshly preparing food, many African communities leave food to ferment. Fermentation of cereals is a traditional method of reducing the microbial contamination of porridges. Beliefs and consumption patterns of fermented food were examined among mothers of children aged under five and health workers in a rural and urban community in Kenya. The majority (83%) of rural mothers reported that their families regularly consumed fermented food and over half (66%) gave their young children fermented food. In the urban area, fewer mothers (56%) reported that their families ate fermented food and only (40%) gave their children some kind of fermented food. Several reasons for the declining use of fermented food were given including education by health workers that fermented foods were bad, declining production and availability, and substitution of traditional foods by commercial products such as soft drinks. Health educators need to consider that mothers may be missing out on a potentially useful means of preventing diarrhoea in their children.