Renal disorders are among the most commonsonographically detected fetal abnormalities.Pyelectasis is one of the most common diagnoses inthe prenatal period. The present study was conductedon 50 fetuses who suffered from antenatal renal pelvisdilatation during the third trimester. 70% of the casesdiagnosed as antenatal renal pelvis dilatation weremales and 30% were females. Idiopathic casesrepresented 74%. Most of cases resolvedspontaneously, as detected by ultrasound done in thefirst month of life. 20% of cases showed stationarycourse that required follow up. Only 10 % of casesneeded surgery.