The stone-free rate declines as stone size increases (5 - 10 mm: 90%, 11 - 15 mm: 79.4%, 16 - 20 mm: 27.8%; p<0, 01), stones that appeared more dense than bone (47.4% compared with 80.8% of less dense stones; p<0.05), smaller infundibulopelvic angle (less than 40 degrees: 67.3%, 40 degrees or more: 87.5%; p<0.05). Conclusion: Stone-free rate after ESWL is adversely affectted by: stone size more than 15 mm, more dense stone, infundibulopelvic angle less than 40 degrees.