Sulforaphane (1), a glucosinolate-derived isothiocyanate found in the cruciferous vegetable broccoli, is considered an anticarcinogenic component. In the present study, the proliferation and apoptosis induction in human lung adenocarcinoma LTEP-A2 cells by 1 was investigated. Compound 1 caused G(2)/M-phase arrest (p < 0.05) and increase of apoptotic cell fraction (p < 0.05) in a time- and dose-dependent manner. Intraperitoneal injection of 1 significantly inhibited growth of LTEP-A2 xenografts in nude mice, and 9 days after tumor cell implantation with 100 mg/kg intraperitoneal injection of 1, the average tumor weights in 1-treated mice was >70% lower than that of the control mice.