Tempe is a fermented soy bean product originally made by Central Javanese people through fermentation with Rhizopus species. Although there is evidence of earlier fermentation of soy, tempe had appeared in the Central Javanese food pattern in the 1700s. Through its extensive use in main meals and snacks, it has led to people in the Jakarta prectinct having the highest known soy intake in the world and accordingly of the isoflavones contained. This provides an unique opportunity to consider the health effects of tempe (and soy), both beneficial and potentially toxic. Apparent health benefits are bowel health, protection against cardiovascular disease, certain cancers (e.g. breast and prostate) and menopausal health (including bone health). The long use of tempe at all stages of life, without recognised adverse effects, suggests it is relatively safe at the levels of intake seen in Central Java. However, further research on soy, both fermented and non-fermented, in Central Java should yield more insight into the mechanisms of action and the safe ranges of intake.