Abstract Objective: To evaluate emergency treatment of obstructing ureteral stones by in situ extracorporeal shock wave lithotripsy (ESWL) during acute renal colic. Patients and Methods: From January 1994 to February 2000, 200 patients (mean age: 42 years) were treated by ESWL (EDAP LT-02) for obstructing ureteral stones causing acute renal colic refractory to medical treatment or recurring within 24 hours of such treatment. Stones were visualised by fluoroscopic imaging and/or ultrasound. Follow-up included radiological and/or ultrasound examinations and lasted three months. Results: Mean stone size was 7 mm (3–20 mm). At three months, 164/200 (82%) patients were stone-free. This rate ranged from 79% to 83% according to the location of the stone, and from 75% to 86% according to the size of the stone. These differences in rate were not significant. Two or three ESWL sessions were required in 79 patients. ESWL was well tolerated in 90% of patients. The only complication was a case of pyelonephritis requiring the placement of a JJ stent, administration of antibiotics, and distant ureteroscopy. The 36 patients, in whom ESWL failed, underwent ureteroscopy ( n=23) or lithotripsy with a Dornier ® machine ( n=13). Conclusion: Non-deferred ESWL for acute renal colic secondary to obstructing ureteral stones has a satisfactory success rate and very low morbidity.