The goal of this study was to determine the factors affecting stone clearance after extracorporeal shock wave lithotripsy (ESWL) for lower caliceal stones. Lower pole stone clearance was investigated in 128 (80 males, 48 females) patients treated with ESWL during 1998-2003 in our clinic. Renal anatomy was determined on standard intravenous urogram. The lower infundibulopelvic angle (LIPA) was measured as the angle between the vertical pelvis axis and the vertical axis of lower infundibulum (Sampaio's method). The mean age of the patients was 42.8 +/- 12.4 (19-77) years. The mean stone diameter and burden were found to be 1.28 +/- 0.58 (0.5-3.5) cm and 1.2 +/- 1 (0-7) cm(2) respectively. The stone-free rate was 62.5% and ESWL was unsuccessful in 16 (12.5%) patients. Thirty-two (25%) patients had residual fragments < or =4 mm retained in lower calices after lithotripsy. The stone clearance was found to be unrelated to stone burden and diameter (P = 0.17 and P = 0.14, respectively). However, there was a significant difference between mean lower pole infundibulum length (P = 0.001), infundibulum width (P = 0.001) and LIPA (P = 0.0001) between stone-free patients and patients with residual fragments. Multivariate logistic regression analysis accepting stone-free as the favourable result also confirmed that LIPA, lower pole infundibulum length and width were factors that significantly affected the outcome. Lower pole anatomy has a significant influence on clearance of fragments after ESWL.