Background/Aims: Unilateral renal ischemia during 30 min causes severe, non-reversible renal damage in diabetic (DM) rats, but not in nondiabetic rats. Hyaluronan (HA) is a glycosaminglycan involved in various forms of renal injury. We examined the role of HA and CD44, a major receptor for HA, in the development of postischemic renal injury in DM rats. Methods: The left renal artery of streptozotocin diabetic Wistar rats was clamped for 30 min. The HA content in the kidneys was measured. A biotinylated HA-binding probe was used to localize HA. Inflammatory cells and other cells expressing CD44 were identified by immunohistochemistry. Results: In ischemic DM kidneys the renal HA-content started to increase already after 24 h and significantly so after 1–8 weeks after ischemia/reperfusion (I/R). The relative water content of the kidneys increased in parallel. HA started to appear in the cortex of ischemic DM kidneys 1 week after I/R. In contrast, the non-DM ischemic kidneys showed no increase of HA and water content after 1–8 weeks after I/R. The tubular cells in the cortex and outer medulla demonstrated increased staining for CD44. In the same compartments the increased numbers of infiltrating inflammatory cells also expressed CD44. Conclusion: HA-accumulation in the renal cortex might contribute to the renal damage seen after transient ischemia in DM rats by promoting inflammation through interaction between HA and CD44 expressing inflammatory cells. Furthermore, HA accumulation may contribute to an interstitial renal edema.