Flow cytometry and laser-scanning confocal microscopy were used to study the effect of sulforaphane (SFN) and 2-oxohexyl isothiocyanate on the growth and viability of mouse leukemia L-1210 and human melanoma ME-18 cells during their exponential growth. Sulforaphane belongs to a group of compounds known as isothiocyanates. Isothiocyanates mainly occur in Cruciferous family. In particular, they occur in many vegetables such as broccoli and their sprouts. SFN and 2-oxohexyl isothiocyanate are potent inducers of detoxication phase 2 enzymes in mouse tissues and murine hepatoma cells in culture. Sulforaphane was shown to induce cell growth arrest in a dose dependent manner, followed by cell death. Sulforaphane induced the cell death via an apoptotic process. Two markers of apoptosis were investigated: phosphatidylserine externalization, which occurs in the early stages of apoptosis, and DNA strand breaks. Our results strongly suggest of chemopreventive activity toward cancer by the induction of apoptosis by SFN and 2-oxohexyl isothiocyanate.