Ureteroscopy is used commonly for ureteric and renal stones. Retrograde intrarenal surgery (RIRS) allows us to treat ureteric and renal stones in all locations with no real contraindications for its use. Increasingly it is being used for larger renal stones and stones in paediatric patients. The technology has evolved from fiberoptic scopes to digital scopes, improving vision, thereby also improving stone free rates. There has been minimisation of scopes with smaller 7.5F flexible ureteroscopes, and more recently with suction attached to them to reduce the intrarenal pressure and temperature. The use of ureteral access sheath and post-procedural stent is generally at the discretion of the surgeon. As the boundaries of RIRS expand, there is evidence to show its successful use in paediatric patients, elderly, pregnancy, obesity, solitary kidney, transplant kidney and large renal stones >2 cm. RIRS can also be used successfully for endoscopic management of upper urinary tract tumours both for diagnostic and therapeutic purposes. In this chapter we have shown the current literature pertaining to the use of RIRS in a variety of complex patients and stone disease with efficacy and complications in these sceneries. RIRS seems to be a safe and efficient method for treatment of these patients and will have expanding role in future through use of modern technology such as use of artificial intelligence, intrarenal pressure and temperature monitoring.