When a calculus is present in the upper urinary tract during pregnancy, the upper tract dilatation seen on radiography and ultrasonography can be due to the calculus or to the pregnancy. This makes the decision on management difficult unless there are associated clinical findings of pain or sepsis. The records of 24 pregnant patients with proved urinary calculi were reviewed. The stone passed spontaneously in 18 patients, and procedures to remove the stone were required in 6 for pain and/or sepsis. With an upper urinary tract calculus and dilatation during pregnancy the deciding factors for intervention were the clinical findings of pain and/or sepsis and not the dilatation alone.