The antihyperglycemic effect of the thiazolidinedione (TZD) class of oral antidiabetic agents is due to their ability to increase insulin sensitivity at the cellular level, which in turn improves the ability of endogenous insulin to regulate glucose utilization by the tissues. Compounds of the sulfonylurea (SU) class act to stimulate insulin production by the pancreas, overcoming insulin resistance by increasing circulating insulin levels. The mechanisms of two kind OADs may be viewed as complementary, offering the opportunity for improved efficacy and durability of effect through coadministration of a TZD and a sulfonylurea.