The consumption of soyfoods is of great interest because of their proposed anticancer and antiatherogenic activity. It has been suggested that the soy isoflavones genistein and daidzein are responsible for these activities. The objective of this study was to determine the variation of the isoflavone content of commercially available packaged tofu by brands and batches. The content of total genistein and daidzein/glycitein aglycones in tofu samples was determined by high-performance liquid chromatography after acid hydrolysis in 23 different brands and different batches of four of these brands. Between different tofu brands the genistein and daidzein/glycitein content varied from 0.07 to 0.34 mg/g and 0.10 to 0.24 mg/g wet weight, respectively. The isoflavone content from batch to batch of the same brand varied between 7 and 28% based on dry weight. Assuming a daily consumption of 30 g soy products, the isoflavone intake could vary between 5.4 and 17.1 mg/day.