We report about 20 inoperable patients with staghorn calculi or residual stones following previous surgery. Follow up to seven years revealed that most were accompanied by gram-negative bacteria (mainly proteus species). All patients received stone prophylaxis regularly (allopurinol, vitamin B 6, KCl, cellulose phosphate). Antibiotics were administered only for short durations. In no case we did observe any serious complications, in only two patients stones increased in size, but one of them was later diagnosed to have hyperparathyroidism.