Despite their proposed health benefits and long history of consumption in Asia, soyfoods have become controversial. In recent years, the benefits of soy have been challenged, and concerns have been raised about possible adverse effects of soy consumption. Underlying most of the benefits and concerns is the presence of isoflavones (phytoestrogens) in soybeans. The evidence reviewed in this article indicates that soy consumption reduces risk of coronary heart disease and, if consumed early in life, potentially breast cancer. Concerns that soyfoods may be contraindicated for breast cancer patients and women at high risk of developing this disease are not supported by the clinical and epidemiologic evidence. The clinical evidence also does not support the notion that isoflavones or soyfoods feminize men. However, some question remains as to their effects in subclinical hypothyroid patients, although soyfoods do not adversely affect thyroid function in healthy subjects. The preponderance of the evidence indicates that for healthy individuals, with the exception of those relatively rare persons with allergies to soy protein, soyfoods can make important contributions to the diet.