This book describes basic information and current applications of flexible ureteroscopy in diagnosis and treatment of renal stones, covering topics on history, anatomy, preoperative preparation, clinical operation, and training for beginners. Basic as well as advanced techniques of flexible ureteroscopy for large renal stones, pediatric patients, and in special situations are presented in details with representative cases and high-resolution illustrations. In addition, disposable, wireless, and robotic flexible ureteroscopy are introduced in details to help readers to learn advanced techniques. It will be a useful reference for urologists, especially for those who are interested in improving their flexible ureteroscopy skills in clinical practice.