Phytoestrogens are plant-derived compounds that may bind to estrogen receptors, but with less affinity than the natural ligand estradiol. They may be biologically active as such or after metabolization in our body. To investigate the occurrence and level of phytoestrogens, scientific literature was screened for data on isoflavones, lignans, stilbenes and coumestans in raw and processed foods of plant origin. The review presents data based both on analytical methods hydrolysing glucosides and non-destructive methods.Many phytoestrogens are phytoalexins. Their production is induced when plants are exposed to abiotic and/or biotic stress. This could explain the rather different levels reported in plants by various investigators, and indicates that many samples are required to describe the levels generally occurring in foodstuffs. The influence of food processing was also considered.