Objective: To compare renal volume in a group of prepubertal and pubertal children with type 1 diabetes mellitus (DM) and either borderline microalbuminuria (BM) or intermittent microalbuminuria (IM) with a matched group of normoalbuminuric (NA) controls with DM.Research design and methods: Twenty-one patients with BM or IM were matched for age, gender and duration of DM with an NA control group. Total renal volume (RV), measured by ultrasound, was corrected for body surface area. Long-term diabetes control was assessed by glycosylated haemoglobin levels.Results: There were no significant differences in age, duration of DM or glycosylated haemoglobin levels between the groups. Those with BM or IM had significantly increased total renal volume (303 +/- 8.4 ml/1.73m(2)) compared to those with NA (276.3 +/- 10 ml/1.73m(2)) (T-40=2.04, P=0.05). Multivariate modelling suggested that this association was independent of potential confounding covariates. While not formally significant (chi (2)(1)=2.53, P=0.12), the frequency of nephromegaly (RV > 300 ml/1.73m(2)) was doubled in children with BM or IM (47.6%) compared to controls (23.8%). Nephromegaly was not found in prepubertal patients.Conclusions: This study suggests that nephromegaly is more common in patients with borderline increases in urinary albumin excretion rates (AER) than those with normoalbuminuria. Prospective follow-up of those with increased renal volume is needed to determine whether nephromegaly is an early marker of incipient nephropathy.