We present 3 case reports to illustrate the variability of outcome of severe fetal posterior urethral obstruction. Two of the described cases support the view that early in-utero decompression of an obstructed fetal urinary system into the amniotic cavity, in the selected patient, will allow adequate lung development and will prevent the development of severe renal dysplasia. It will not prevent the abdominal wall deformity of the prune belly syndrome. The evidence suggests that to allow maximum time for lung development and to prevent increasing renal dysplasia, drainage should be performed before 18 weeks of gestation. To obtain maximum effect, this drainage should continue until at least 32-33 weeks' gestation, so that the possible respiratory problems of prematurity would not be severe enough to compound the degree of lung hypoplasia which might be present. Case 3 supports our view that an endoscopic approach to in-utero drainage of the urinary tract has the advantage of achieving drainage with minimal risk to both mother and fetus.