Résumé : Fetal renal pelvis dilatation is a frequent abnormality that has been observed in 4.5% of pregnancies. The majority of these cases have a tendency to resolve during infancy. Nevertheless, fetal renal pelvis dilatation may be due to significant structural abnormalities such as pelvi-ureteric junction stenosis or vesico-ureteral reflux that may adversely affect renal function or cause urinary infection or sepsis. This review article aims to summarize the data regarding fetal renal pelvis dilatation and to analyze controversial attitudes in the light of the various lines of practice, and to present rational antenatal and postnatal investigation strategy. © 2005 Elsevier B.V. All rights reserved.