A total of 110 patients with upper ureteral calculi was admitted to a prospective trial and randomly allocated to 2 groups: 1 group treated with in situ extracorporeal shock wave lithotripsy (ESWL) and 1 group treated with ureteral manipulation before ESWL. All patients had solitary upper ureteral calculi without urinary infection. The stones had to be smaller than 1 cm. and located more than 2 cm. lateral to the spine. ESWL was performed with the Dornier HM3 lithotriptor. One patient in the in situ ESWL group had to be treated twice because disintegration of the stone was insufficient after the initial treatment session. All other patients underwent only 1 treatment session. Because 16 patients were lost to followup, 94 were evaluable for the analysis of immediate and long-term results. For disintegration of the stones in situ ESWL needed significantly more shock waves (1,844 +/- 639 versus 1,297 +/- 473, p < 0.001) and a higher voltage (19.5 +/- 1.4 versus 18.7 +/- 0.9 kv., p < 0.001). There were no severe complications in either treatment group. At 3 months 44 of 46 patients (96%) after in situ ESWL and 45 of 48 (94%) after ureteral manipulation before ESWL were free of stones. In view of these results it is suggested that uncomplicated upper ureteral calculi (as defined previously) should be treated first with in situ ESWL, thus, avoiding an invasive procedure.