Inhibition of the enzyme histonedeacetylase (HDAC) is emerging as a novel approach to the treatment of cancer. A series of novelsulfonamidederivatives were synthesized and evaluated for their ability to inhibit human HDAC. Compounds were identified which are potent enzyme inhibitors, with IC50 values in the low nanomolar range against enzyme obtained from HeLa cell extracts, and with antiproliferative