b＞Background/b＞ A Current diagnosis of neonatal acute kidney injury relies on serum creatinine (Cr) and urine output. However, serum Cr levels are affected by maternal Cr levels for several days after birth and may vary according to muscle mass, age, and hydration state, but urinary Neutrophil Gelatinase-associated Lipocalin (NGAL)/Cr ratio and serum Cystatin C (CysC) are not affected by maternal level of those. We compared serum Cr and urinary NGAL/Cr ratio and serum CysC, as new emerging renal biomarkers, in VLBWIs. b＞Methods/b＞ Urinary NGAL/Cr ratio, serum Cr and CysC were measured sequentially after birth. Blood samples were taken from the umbilical cord at birth and from a peripheral vein after birth. All urine samples were collected within 24 h after collection of the blood samples. A total of 571 samples from 139 VLBWIs were collected and analyzed. The samples were stratified into five groups on postnatal age (at birth, 2-3, 4-7, 8-21, and ＞21 days). b＞Results/b＞ At birth, there were no correlations between serum Cr and serum CysC or urinary NGAL./Cr ratio, but there was significant correlation between serum CysC and urinary NGAL/Cr ratio (r = 0.189, p = 0.026). Serum Cr was positively correlated with serum CysC and urinary NGAL/Cr ratio (p 0.001) in three groups on postnatal age (4-7, 8-21, and ＞21 days). In samples collected at birth, urinary NGAL/Cr ratio was negatively correlated with gestational age and birth weight (p 0.001), but serum CysC was not. Except samples collected at birth, postnatal age was negatively correlated with serum Cr and urinary NGAL/Cr ratio (p 0.001), but not with serum CysC. b＞Conclusions/b＞ In the present study, serum Cr is positively correlated with serum CysC and urinary NGAL/Cr ratios after more than three days of birth. Serum CysC is more independent than urinary NGAL/Cr ratio in VLBWIs.