Isothiocyanates (ITCs) from cruciferous vegetables have been shown to be effective in blocking initiation as well as progression of a range of chemically-induced tumors in animal models. In this study, sulforaphane, the most extensively studied ITC, was found to suppress the growth of T24 bladder cancer cells in vitro in a dose-dependent manner. Sulforaphane inhibited the proliferation of T24 cells with IC50 values 26.9 and 15.9 µM following 24 and 48 h treatments. Sulforaphane (5-20 µM) induced early apoptosis and blocked cell cycle progression at G0/G1 phase which was associated with upregulation of cyclin-dependent kinase inhibitor p27 expression. These results support a role for sulforaphane as an effective agent in the chemoprevention of bladder cancer.