Consumption of Brassicaceae family vegetables is related with reduced risk of certain cancers in humans. This is due to presence of glucosinolates in those vegetables. In the present study, four major glucosinolates (sinigrin, glucoraphanin, glucotropaeolin and gluconasturtiin) were identified and quantified in five popular Brassica species found in Sri Lanka by High Performance Liquid Chromatography (HPLC) combined with photodiode-array detection (PDA). Brassica species selected for this study was broccoli (Brassica oleracea var. italica), white cabbage (Brassica oleracea var. capitata), red cabbage (Brassica oleracea var. capitata), radish (Raphanus sativus) and cauliflower (Brassica oleracea var. botrytis), The results show that the radish tubers contain highest concentration of glucoraphanin (39684.0±8.7µg/g), which is one of the most well-known glucosinolates for inducing anticarcinogenic reactions in humans. Glucoraphanin is higher in red cabbage (4221.3±1.7 µg/g), than white cabbage (1557.0±9.0 µg/g). Gluconasturtiin was not found in white cabbage and radish tubers, whereas red cabbage contains trace amounts. Cauliflower contain high amount of sinigrin than other species. It is interesting to note that the type and content of individual glucosinolate varied according to the Brassica species as well as the plant part.