The random urine albumin:creatinine (Ua:Uc) ratio was measured in 139 healthy children from newborn to age 4 years using the immunonephelometric method. This was shown to vary with age, the mean for neonates being 5.24mg/mmol (2SD range: 0.54-14.95mg/mmol) decreasing to 1.34mg/mmol (2SD range: 0.55-3.29mg/mmol) for the 2-4 years age range. The values for newborn to 6 months was significantly higher than the older age group (p less than 0.000001). 14 children with structural renal disease were then studied to determine the value of the random Ua:Uc ratio in detecting glomerular injury. This was found to be abnormal in children with glomerular filtration rate (GFR) less than 80ml/min/1.73m2 as well as in some children with complex bilateral renal structural abnormalities. Further longitudinal studies are required to determine the usefulness of this ratio in predicting progressive glomerular injury in this group of patients.