Sulforaphane is an anticarcinogenic isothiocyanate derived from 4-methylsulfinylbutyl glucosinolate (glucoraphanin), which is abundant in broccoli ( Brassica oleracea var. italica ) florets. However, some breakdown products from alkenyl glucosinolates present in many broccoli cultivars, particularly oxazolidine-2-thione hydrolyzed from 2-(R)-hydroxy-3-butenyl glucosinolate (progoitrin), have potentially harmful effects on human and animal health. The main objective of this study was to improve the glucoraphanin concentration in F 1 hybrids by cross-breeding with inbred lines and doubled haploids. Glucoraphanin concentrations in 31 of the 61 F 1 hybrids were significantly higher ( P = 0.05) than that of the commercial cultivar (Youxiu) with the highest concentration of glucoraphanin (4.18 μmol·g −1 dry weight) among eight reference cultivars. Sixteen of the F 1 hybrids had glucoraphanin concentrations 3-fold higher than that of ‘Youxiu’. Alkenyl glucosinolates were not detected in the new hybrids as a result of the parents having few of these compounds but were found in five reference cultivars. Most F 1 hybrids showed moderate indole glucosinolate concentrations and acceptable commercial traits. IL609 and IL702.2 were determined to be promising parental lines as a result of the high glucoraphanin concentration that they and their offspring contained. The findings also indicated that some F 1 hybrids do not show the high-glucoraphanin character of their parents; consequently, evaluation of these F 1 hybrids for their glucosinolate content is required for breeding high-glucoraphanin broccoli.