The title compound, C6H6N2Cl2O4S2, is one of the carbonic anhydrase inhibitors and can be clinically applied for the treatment of glaucoma. The crystal belongs to space group C2/c with the cell dimensions a = 17.216(1), b = 7.9030(5), c = 16.457(2)Å and β = 94.671(3)°. The final R value is 0.037. Two amino groups are on the same side of the phenyl rings. Although all nitrogen and oxygen atoms are involved in hydrogen bonds, chlorine atoms are not involved. 2003 © The Japan Society for Analytical Chemistry.