Steroid sulfatase (STS) is an attractive target for a range of oestrogen- and androgen-dependent diseases. In search of novel chemotypes of STS inhibitors, we had previously identified nortropinyl-arylsulfonylureas 1; however, while these compounds were good inhibitors of purified STS (lowest K(i)=76 nM), they showed only weak inhibition of STS activity in cells (lowest IC(50) around 2 microM). Extended structure-activity relationship studies involving modification of the phenylacetyl side chain and replacement of the nortropine element by simpler scaffolds led to the discovery of N-acyl arylsulfonamides, more specifically N-(Boc-piperidine-4-carbonyl)-benzenesulfonamides, as STS inhibitors, some of which exhibit improved cellular potency (best IC(50)=270 nM).