In this study, aldose reductase (AR) was purified from sheep kidney using chromatographic methods and examined the interactions between some sulfonamides and the enzyme. According to results, sulfonamides display effective inhibitor features for sheep kidney AR with IC50 values in the range of 37.27-87.65 mu M and K(i)s in the range of 25.72 +/- 6.45 to 73.56 +/- 17.49 mu M. The sulfonamides displayed different inhibition mechanisms. It was found that studied all compounds displayed non-competitive inhibition type except for 5-chlorothiophene-2-sulfonamide (1). It showed competitive inhibition. Among these compounds, 2,5-dichlorothiophene-3-sulfonamide compound (2) was showed the most potent AR inhibitor (K-i: 25.72 +/- 6.45). These compounds may be useful in the treatment of diabetic complications.