In this study, starting from a lead compound discovered by virtual screening, a series of novel heterocyclic substituted benzenesulfonamides were designed and synthesized as new carbonic anhydrase IX (CA IX) inhibitors. Some compounds exhibited potent inhibitory effects against CA IX (in the low nanomolar range) as well as high selectivity against other carbonic anhydrase isozymes (CA I and CA II). The most potent and selective compound 27 could inhibit CA IX in the subnanomolar level with IC50 of 0.48 nM, which increased the potency by about 40-fold against CA IX compared with the lead compound 26, and presented more than 10(3) fold selectivity over CA I and CA II. The structure-activity relationship (SAR) based on the docking experiments further elucidated the effects of the compounds on the bioactivity and selectivity.