OBJECTIVE To investigate perinatal risk factors that may be associated with impaired renal function during the first 2 weeks of life. METHODS The case notes of 150 neonates of gestational age (GA) 34-36 weeks and 494 of GA > 36 weeks were studied. Clinical risk factors were retrieved, along with indices of renal function: serum creatinine (SeCr), fractional excretion (FE) of sodium (FENa) and potassium (FEK), and the urinary calcium to creatinine ratio (UCa/UCr). Associations were identified by multiple and logistic regression analysis. RESULTS In infants with GA > 36 weeks, raised SeCr was related to perinatal stress, odds ratio (OR): 1.9, confidence interval (CI): 1.2-2.9, p < 0.05, and to duration of treatment with aminoglycosides (AGs) (t = 2.4, p < 0.01); FEK was associated with jaundice (t = -3.1, p < 0.01), and FENa with duration of AGs treatment (t = 2.6, p < 0.01). Full-term neonates with both hypoxic-ischemic encephalopathy (HIE) and AGs administration had an 80% increase in OR for impaired SeCr levels. In infants of GA 34-36 weeks, SeCr was related to perinatal stress (OR: 9, CI: 1.3-38, p < 0.05), FEK to jaundice (t = -2.1, p < 0.05), and FENa to duration of AGs administration (t = 2.2, p < 0.05) and antenatal steroid treatment (OR: 0.8, CI: 0.6-0.95, p < 0.05). CONCLUSIONS In neonates, renal impairment, being multifactorial in origin, may be caused by the additive effect of different perinatal factors. The strong negative relationship observed between jaundice and K excretion merits further investigation.