The histories of 72 recipients of renal transplants who had been followed three months to seven years or until death, were reviewed to determine the incidence of urinary tract infection. This review was made to evaluate the role of primary diagnosis, donor source, technique of urinary drainage, urologic complications, and duration of catheter drainage in the occurrence and persistence of urinary tract infection. Definitions A urinary tract infection was defined as a quantitative determination on urine culture of greater than 100,000 pathogenic organisms per milliliter from a voided urine or catheter specimen. Repeated counts of less than 100,000 per milliliter of the same pathogen were interpreted as significant and are included as positive. Random urinary cultures of 100,000 per milliliter or less of nonpathogenic organisms such as diphtheroids, micrococcus, or Döderlein's bacillus, combined with several negative reports in the same patient, were interpreted as insignificant. Recipients of renal grafts with