The Italian-style Mediterranean diet has been defined as healthy by epidemiologists and nutritionists. Besides being low fat, the Mediterranean diet is rich in biologically active minor compounds. Among these, phytoestrogens seem to have an impact on the prevention of chronic degenerative disease. It is important to understand how this occurs. The in vitro estrogenic activity of crude extracts from typical Mediterranean foods was tested using a yeast estrogen screen (YES), containing human estrogen receptor. Species belonging to Leguminosae, Apiaceae, Graminaceae, Iridaceae, Chenopodiaceae, Cruciferae and Solanaceae showed the greatest number of positive responses. These species include some foods which are traditionally widely consumed, such as beans and other legumes, tomatoes, cabbage, carrots and some cereals. The highest activity was found in the more polar extracts (aqueous, methanol and chloroform: methanol) indicating that polar compounds are mainly responsible for the estrogenic activity. This is also supported by the traditional cooking practices. According to data from in vitro tests, the estrogenic activity is present in numerous plants which are commonly used as food in the Mediterranean diet. Vegetable foods rich in phytoestrogens, as in the Mediterranean tradition, may contribute to the maintenance of health status.