We have previously suggested that differences in cancer incidence between Polynesians (including Maoris and people from several Pacific islands) and Europeans in New Zealand may at least partially relate to differences in the species of food plants (fruits, vegetables and cereals) preferentially eaten by these groups. Twenty-five food plants that are typically eaten in different amounts by these two population groups were selected for detailed study. Antimutagenic properties of three extracts from each of the selected plants were investigated using a preincubation mutagenicity assay with Salmonella typhimurium strain TA1538 against the mutagenicity of the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). The data revealed strong antimutagenic properties in several of the food plants commonly eaten by Polynesians, especially rice, watercress, pawpaw, taro leaves, green banana and mango. Using the New Zealand food database, a number of nutrients and micronutrients with antimutagenic and anticarcinogenic potential were identified from the selected food plants. Some of these were tested for antimutagenic potential in parallel experiments to those done with the food plant extracts. Although some of these micronutrients are antimutagens against IQ, their concentrations in the food plants failed to explain the protection against mutagenicity found in the experiments with extracts of the food plants. Thus, other types of chemical, not identified in the database, must be leading to antimutagenesis. Possible active molecules include chlorophylls, carotenoids, flavonoids and coumarins, many of which are also known to be anticarcinogens. If human cancer data are to be interpreted in terms of cancer protection, these components need urgently to be quantified in food plants in the New Zealand diet, especially in those food plants eaten in large amounts by Polynesians.