BACKGROUND Renal failure is common among older patients with sickle cell disease; this is preceded by subclinical glomerular hyperfiltration. Data about renal function of adults with sickle cell disease have been reported, but data on children is scarce, especially when comparing heterozygotic and homozygotic patients. OBJECTIVE The goal of this study was to investigate the glomerular filtration rate of heterozygotic and homozygotic children with sickle cell disease. METHODS The glomerular filtration rate of 11 children with sickle cell disease [7 homozygotic (SS) and 4 heterozygotic (SC)] with a mean age of 11 years (standard deviation: ± 5 years) was evaluated using standard laboratory techniques. Results are presented as descriptive analysis. RESULTS Our results suggest that glomerular hyperfiltration is present in children with sickle cell disease; this is more evident in homozygotic than heterozygotic children. CONCLUSIONS There is evidence of a need to monitor the renal function of children with sickle cell disease when special attention should be paid to homozygotic patients.