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Objective: This study was conducted to compare the potential inhibitory effect of ATP-dependent K + channel blockers, glibenclamide and chlorpropamide on diazoxide-induced relaxation of iso- lated rat ileum. Material and Methods: The study was performed on rat ileum connected to an isotonic transducer and the contractions were recorded on one-channel MD 2 recorder. In this study the relaxant effect of diazoxide on KCl-induced precontracted rat ileum, and its inhibition by different concentra- tions of glibenclamide and chlorpropamide were studied. Results: Diazoxide (10 -5 -10 -3 M) produced dose-dependent relaxation. EC 50 for diazoxide-induced relaxation was 8 x 10 -5 M. Neither glibenclamide nor chlorpropamide had any effect on the resting tension of the rat ileum preparation. Both glibenclamide and chlorpropamide reversed diazoxide- induced relaxation. The pA 2 values for glibenclamide and chlorpropamide reversal of diazoxide induced- relaxation were 6.3 and 5 respectively. Conclusion: The results confirm that the inhibitory effect of glibenclamide on diazoxide-induced relaxation in rat ileum is higher than that of chlorpropamide.