Aims: To determine changes in relative peak intensities of mass-to-charge ratio (m/z) between 2,000 and 15,000, which are difficult to evaluate by 2-dimensional gel electrophoresis, SELDI-TOF-MS (surface-enhanced laser desorption/ionization time of flight-mass spectrometry) proteomic changes in rat models of adriamycin nephropathy with or without AST-120 were investigated. Methods: A normal group (n = 5), an adriamycin nephropathy group (n = 9), and an adriamycin nephropathy + AST-120 group (4 g/head/day) (n = 9) were established in SD rats. Anion exchange chips, Q10, washed by 50 m M Tris-HCl pH 8 as a ProteinChip and sinapinic acid were used. The mass range between 2,000 and 15,000 Da was measured. Twenty to 34 weeks after adriamycin 3 mg/kg injection, the adriamycin nephropathy + AST-120 group (plasma creatinine value: 2.1 ± 0.8 mg/dl) clearly demonstrated slight renal dysfunction compared with that in the adriamycin nephropathy group (5.4 ± 2.0 mg/dl). Results: The relative intensities in the adriamycin nephropathy group were significantly higher in 7 peaks (such as 8,640, and 8,822 Da) and lower in 8 peaks (such as 4,188, and 8,358 Da) than those in the normal group. The relationship between the relative intensity of peaks and the plasma creatinine value demonstrated a positive correlation in 11 peaks (such as 8,640, and 8,822 Da), and a negative correlation in 6 peaks (such as 4,188 and 8,358 Da). Although the relative intensities of peaks in the adriamycin nephropathy + AST-120 group were between that of the adriamycin nephropathy group and that of the normal group, the relative intensities of 4 peaks (such as 3,664 and 5,179 Da) in the adriamycin nephropathy + AST-120 group demonstrated higher values than in the two other groups. The m/z 3,664 peak was purified and identified as a C-terminal fragment of apolipoprotein C-III. Conclusion: Low-molecular proteins and peptides in plasma in this chronic renal failure model showed not only increases but also decreases in some peaks. The relative intensities in some peaks increased in the adriamycin nephropathy + AST-120 group more than in the two other groups. One of these peaks was identified as the apolipoprotein C-III fragment. The relationship between these changes and the prevention of progression of chronic renal failure by AST-120 remains to be established.