Glucosinolates (GSLs) are a class of sulfur-containing compounds found predominantly in the genus Brassica of the Brassicaceae family. Certain edible plants in Brassica, known as Brassica vegetables, are among the most commonly consumed vegetables in the world. Over the last three decades, mounting evidence has suggested an inverse association between consumption of Brassica vegetables and the risk of various types of cancer. The biological activities of Brassica vegetables have been largely attributed to the hydrolytic products of GSLs. GSLs can be hydrolyzed by enzymes; thermal or chemical degradation also breaks down GSLs. There is considerable variation of GSLs in Brassica spp., which are caused by genetic and environmental factors. Most Brassica vegetables are consumed after cooking; common cooking methods have a complex influence on the levels of GSLs. The variationof GSLs in Brassica vegetables and the influence of cooking and processing methods ultimately affect their intake and health-promoting properties.