The in vitro effects on human articular chondrocytes were evaluated for a series of N-benzo[d]isothiazol-3-yl-amidines, bearing as pharmacophoric moiety the nonacidic isosteric nitrogen analogue of the carboxylic group. The aim was to verify their effectiveness in articular diseases, such as arthritis. Human chondrocytes were treated with IL-1beta in the presence of a series of N-benzo[d]isothiazol-3-yl-amidines at a concentration of 100 microg/mL. After 120 h, the amount of glycosaminoglycans (GAGs), the production of nitric oxide (NO) and the inhibition of metalloproteinases (MMP-3) and prostaglandin (PGE2) were measured. Nitrite production induced by inflammatory IL-1beta on cultured chondrocytes was inhibited by the N-benzo[d]isothiazol-3-yl-amidines tested, in particular by N-benzo[d]isothiazol-3-yl-benzamidine, which was the most active. Concerning the effects on GAGs, all the tested benzisothiazolylamidines, and in particular N-benzo[d]isothiazol-3-yl-acetamidine, prevented the depletion of proteoglycan induced by IL-1beta. Inhibitory effects of the tested compounds on MMP-3 activity and on PGE2 production were also observed.