Surveillance studies using molecular typing methods help clinicians assess the rate of potential spread of pathogens. The rate of cross transmission of uropathogens among patients on a urological ward was investigated. Urine samples were collected from 144 patients with urinary catheters and a significant bacteriuria. In a subgroup of 54 of these patients, cultures from a rectal swab were also made. Typing by PFGE, RAPD or bacteriocins showed that 41% of uropathogens were related and represented by 38 typing patterns. Endogenous infection was present in 30% and exogenous infection in 38% of isolates. Altogether, there was a high rate of clonal relationship amongst uropathogens in our urological ward and we conclude that hygienic means and measures are far from being optimal.