Inhibition of histone deacetylase (HDAC) provides a potential target for cancer treatment. Histones are components of the core proteins of nucleosomes, and acetylation and deacetylation of these proteins play a role in the regulation of gene expression. HDAC activity is known to be increased in many types of malignant cells; HDAC inhibitors have been shown to induce differentiation, cell cycle arrest, and apoptosis in cultured tumor cells. Since this tumor-associated mechanism is common to many types of cancer, HDAC may have a broad role in cancer treatment.