A review of the molecular mechanisms of nickel carcinogenesis has been compiled. This work is based upon approximately 20 years of research conducted in my laboratory. Molecular mechanisms of nickel carcinogenesis are considered from the point-of-view of the uptake of nickel, both soluble and insoluble particles in cells, its dissolution and its effects on heterochromatin. Molecular mechanisms by which nickel induces gene silencing in cells by DNA hypermethylation in mammalian cells and by inhibiting histone acetylation in yeast cells are also discussed.