Three children with equivocal pelviureteric junction obstruction are described. The renal pelves were only slightly dilated and emptied well with posture change or diuresis, but there was disproportionate dilatation of the calices. On direct puncture perfusion of the pelvis there were repeated high pressure contractions which resulted in emptying, but basal pressure remained normal. This condition appears to be analogous to the partially obstructed but compensated bladder.