A number of 2,4-thiazolidinedione derivatives of aryl-substituted cinnamic acid were synthesized and studied for their antihyperglycemic activity in neonatal streptozotocin-induced diabetic Wister male rats. Substitution of the aryl ring resulted in higher activity. 3-(2,4-Dimethoxyphenyl)- 2-{4-[4-(2,4-dioxothiazolidin-5-ylmethyl)phenoxy]-phenyl} acrylic acid methyl ester (Thz7), was found to be most active compound in this series which showed that disubstitutions on aryl ring by electron releasing groups were found suitable for promising antihyperglycemic activity. Increase in the ester carbon chain length decreased the activity.