AIM: Protein energy malnutrition is common in children with chronic renal failure (CRF) and may negatively impact on clinical outcome. Although the aetiology of malnutrition is multifactorial, descriptive information on body composition may guide nutritional interventions aimed at optimising nutritional status. METHODS: This prospective cohort study in children with CRF was conducted from April 1999 to November 2000. Patients were categorised according to their glomerular filtration rate (GFR) into CRF and end-stage renal failure (ESRF). Body composition was assessed based on anthropometry, total body potassium (TBK), total body protein (TBP) and dual X-ray absorptiometry (DEXA). RESULTS: Fifteen patients (10 male, 5 female; mean age: 13.4 +/- 4.3 years) were studied, including eight patients with CRF (mean GFR: 17.0 +/- 7.2 mL/min/1.73 m(2)) and seven patients with ESRF (mean GFR: 6.4 +/- 1.7 mL/min/1.73 m(2)). Patients in both groups (n = 15) had deficits in height and TBP (mean z-score height-for-age: -1.19 +/- 1.05, P < 0.01; mean z-score TBP: -0.71 +/- 0.71, P < 0.05). There were no significant differences in weight, height, fat-free mass, TBK and TBP between patients with CRF and ESRF. CONCLUSIONS: Linear growth impairment and decreased TBP are common in children with chronic and ESRF. TBK and DEXA may underestimate the degree of malnutrition in these patients.