A 58 year-old woman developed an acute renal failure very quickly after ingestion of two 500 mg tablets of ciprofloxacin, without any other identifiable risk factor. Renal biopsy was performed. No sign of acute interstitial nephritis was observed but tubular lesions were found, accompanied by deposits of a brown-yellowish substance identified by infrared microscopy as a ciprofloxacin salt. The outcome was favourable. This observation gives the opportunity to remind the different forms of quinolone-induced renal injury and to discuss the possible ways for preventing renal side-effects related to the quinolone use.