Some biomolecules essentially from plants or fungi have been shown to exhibit oestrogenic properties. These are prenyl-flavanones, coumestans, resorcylic acid lactones, isoflavones and lignans. Their oestrogenic characteristics have been exploited in medicinal preparations for specific physio-pathological situations like menopause, contraception or osteoporosis. However, the oestrogenic substances are not required for the general populations. Indeed, generally speaking, in animals and humans, oestrogenic effects can be assimilated to endocrine disruptions and should be avoided. In this chapter are related the toxicological effects of plant biomolecules with oestrogenic effects. This is performed by first describing the physiological roles of oestrogens in healthy and sick subjects. Then the actual exposure to oestrogenic biomolecules will be estimated with references to the historical situation. This will lead to proposals to reduce such an exposure. Afterward, the toxicological information actually recorded on animal models by international organizations will be exposed before relating the data presently available in humans. Finally, it will be shown that oestrogenic biomolecules can also exhibit other deleterious effects, reinforcing the need to reduce the animal and human exposures.