Between January 1975 and March 1980, 19 pregnant patients with urinary calculi were admitted to hospital, they constituted 0.23% of all women delivered at the Hôpital St-Luc during that period. The symptoms were characteristic: pain in the flank and right lower quadrant, hematuria, frequency and dysuria. Noninterventional therapy was successful in 14 patients. Two patients were operated upon during pregnancy without complications. Ultrasonography is a useful diagnostic procedure during the first trimester. Pyelography should be considered only after adequate time has elapsed to allow spontaneous elimination of the calculi and, if used, one exposure before and one 30 minutes after injection of the contrast material well ensure the radiation dose is low enough to avoid causing any fetal abnormality. The authors believe that treatment must be individualized depending on the location and size of the calculus, the degree of obstruction, presence of infection, age of the fetus and condition of the patient. Spontaneous elimination after hydration and analgesia is the ideal, lumbar ureterolithotomy or basket extraction can be considered, although surgical procedures are best postponed until the postpartum period.