Flexible ureteroscopes and their accessory working instruments have undergone tremendous design advances since the earliest reports in the 1960s. These changes have allowed for the expansion of indications for flexible ureteroscopy with the emphasis now on therapeutic and not just diagnostic applications. This report covers 290 procedures done with actively deflectable, flexible ureteroscopes on 222 patients. Followup averaged 11.2 months in 228 patients, while the remaining 62 were followed by the original referral center. Included were 154 procedures for stones and 79 for tumors or filling defects. Of the procedures 149 were performed with the patient under local anesthesia with sedation, while 128 were done with use of general anesthesia. The procedure was done in only 22% of the cases for purely visual diagnosis without any interventional manipulation. More than 42% of the cases involved stone retrieval or lithotripsy, in which case the laser was most commonly used (56 cases). The total success rate was 95.5%, and the most common complications were colic or pain in 9% and fever in 6.9%. A stricture developed in 2 patients. A stent was left in more than 93% of the patients and the usual postoperative stay was less than 3 days. With the introduction of even more improved instruments, flexible ureteroscopy should continue to gain ground as an option for the management of upper urinary tract pathology.