Inhibition of histone deacetylases (HDACs) is emerging as a new strategy in human cancer therapy. Novel 2-aminophenyl benzamides and acrylamides, that can inhibit human HDAC enzymes and induce hyperacetylation of histones in human cancer cells, have been designed and synthesized. These compounds selectively inhibit proliferation and cause cell cycle arrest in various human cancer cells but not in normal cells. The growth inhibition of 2-aminophenyl benzamides and acrylamides against human cancer cells in vitro is reversible and is dependent on the induction of histone acetylation. Compounds of this class can significantly reduce tumor growth in human tumor xenograft models.