The history of a patient with signs of urinary tract obstruction in utero is presented. After this presentation pathophysiologic, diagnostic and therapeutic aspects of prenatal detected obstructive malformations of the urinary tract are discussed. Obstructions of the fetal urinary tract may cause damage to the developing renal parenchyma, impairment of the normal lung development and fetal growth retardation. The seriousness of obstruction and the time of appearance during pregnancy determine the severity of the damage to the unborn child. Optimum management in case of prenatal detected obstructive uropathies needs good information about renal function of the fetus, the presence of other structural defects or chromosomal abnormalities and also the maturity and state of development of the lungs. Besides careful ultrasonography of the fetus invasive methods of investigation may be necessary. In case of fetal obstructive uropathy intrauterine decompression or extrauterine decompression after an induced premature delivery can be considered. However a good renal function and the absence of other severe structural or chromosomal malformations are necessary. When the gestational age has come to 32 to 34 weeks and the lungs are mature enough decompression of the urinary tract after an induced premature delivery can be done. When pregnancy is less than 32 weeks of gestational age and the lungs are immature intrauterine decompression is possible. The most used technique of intrauterine decompression so far is insertion of a percutaneous amniotic-bladder catheter. Antenatal detected obstructive abnormalities of the fetal urinary tract need optimum perinatal care besides good information and support of the parents.