Cystine uroliths are a sequela to cystinuria an inherited renal tubular defect in reabsorption of cystine and some others amino acids. The present study report two cases of cystine uroliths presented to the Veterinary Hospital at the University of Londrina during the past four years. A 5-year-old intact male Mastiff dog was presented with dysuria and pollakiuria of 20 days duration. The X-ray revealed a radiodense urolith measuring 2cm. Cystine crystals were observed in urine sediment preparation, and a diagnosis of cystinuria was made. Uroliths were removed surgically from the bladder and a quantitative mineral analysis revealed 100% cystine urolith. A dietary management started for prevention of recurrence. One month after surgery the uroliths signs recurrence and another cystotomy were performed and a dietary management started. The animal had several urinary infections during treatment. Nine months later the dog presented complete outflow obstruction and resulted in cystotomy and urethrostomy. The other dog, a 9 year-old intact male Pinscher was presented with dysuria, pollakiuria and post-renal uremia due to outflow obstruction. Urohydropropulsion and cystotomy were performed, the uroliths were removed and a quantitative mineral analysis revealed 100% cystine uroliths. Five months later the first recurrence occurred and another cystotomy was performed, nine months later the dog had the second recurrence and the uroliths were surgically removed. One year after the last surgery the uroliths signs recurrence and cystotomy was performed for the fourth time. Dietary management was prescribed, but unfortunately the owner could not afford the treatment. Eight months after the last procedure the dog presented outflow obstruction and urethrostomy was performed. The dog died during the anesthetic procedure. Because cystinuria is an inherited metabolic defect and cystine uroliths recur in a high percentage within 2 to 12 months following surgical removal, prophylactic therapy should be considered to promote cystine urolith dissolution and that requires careful and planned monitoring by urinalysis, radiography and ultrasonography.