Extra corporeal shockwave lithotripsy (ESWL) is the treatment of choice for the majority of renal stones, however, it has the lowest success rate in complete clearance of stones located in the lower pole. We assess whether pelvi-calyceal height is a useful measurement in predicting successful stone clearance from the lower pole. A total of 105 patients with a solitary lower pole calculus of less than 20 mm treated with ESWL were reviewed. Stone size, location and pelvi-calyceal height were measured by intravenous urogram. Success was defined as complete stone clearance. Fifty-four patients (51.4%) had successful treatments, with the remaining 51 (48.6%) having incomplete stone clearance (including two patients in whom treatment had no effect). There was a statistically significant difference (P<0.0001) in pelvi-calyceal height between the two groups. Mean pelvi-calyceal height in patients with complete stone clearance was 15.1 mm (SD=3.9) compared with 22.9 mm (SD=5.2) for those with incomplete clearance. Pelvi-calyceal height is a useful predictor of success when treating lower pole renal stones with ESWL.