Hemodialysis (HD) patients are frequently in a state of increased oxidative stress, and hyperglycemia appears to be a major factor. We recently found that oxidized human serum albumin (HSA) is a reliable marker of oxidative stress in HD patients. However, the issue of whether oxidized HSA is associated with the progression of oxidative stress in HD patients with or without diabetes is not clear. In the present study, we examined the effect of a qualitative modification of HSA in HD patients with or without diabetes. Blood samples from 10 HD patients with diabetes, 7 HD patients without diabetes, and 10 healthy age-matched controls were examined. The increase in plasma protein carbonyl content and advanced glycation endproducts (AGEs) in HD patients was largely due to an increase in the levels of oxidized HSA. Furthermore, these increases were greatest in HD patients with diabetes. Purified HSA from HD patients (non-DM-HSA) was carbonylated and AGE-modified. The amount of modified HSA was the highest in HD patients with diabetes (DM-HSA). Carboxy methyl lysine (CML)-modified HSA triggered a neutrophil respiratory burst, and this activity was closely correlated with the increase in the CML/HSA ratio. These findings indicate that uremia plays an important role in the progression of oxidative stress in HD patients via an increase in CML-modified HSA. They also indicate that diabetic complications further exacerbate the progression of oxidative stress by further increasing the amount of these modified HSA molecules.