Nowadays, toxicological studies are contributing to human health more than ever. Reports on the toxicological studies of plant proteins, which are continuously growing in number in the literature, have been reviewed. Two important aspects are discussed: dietary safety evaluation, including toxicity tests and the maximum daily intake allowance, and the appropriate proportion in our daily diets of proteins from traditional foods and of new proteins from plant sources not traditionally employed as foods. Water hyacinth leaf proteins, sweet lupin proteins and canola proteins have not been shown to be toxic, although they are not traditionally employed as food proteins. These findings are very important for exploiting valuable new protein sources that are suitable for human or animal consumption and applicable to the food industry. Acutely toxic proteins, including lectins, ribosome-inactivating proteins, inhibitors of proteolytic enzymes and glycohydro-lases, have been isolated from plant materials and identified. Their toxicities and molecular characteristics have been described. The toxicity of proteins depends upon their specific native structures. Once they are denatured by appropriate treatment, such as heating, their toxicity can be reduced or even eliminated. These findings indicate that raw materials that contain this kind of toxic protein are not edible. However, after proper processing, they may be suitable for human or animal consumption. Although the toxicities of type 2 ribosome-inactivating proteins reported by different authors vary, the maximum dosages are still trace amounts. Copyright © 2011 John Wiley & Sons, Ltd.