Abstract A gentamicin-resistant strain of Klebsiella aerogenes was isolated from the urine of 17 patients out of 237 admitted to a male urological ward between Jan. 21 and May 9, 1977. The factors most frequently associated with K. aerogenes in the urine were catheterisation and antibiotic therapy. Often the epidemic strain (type K16) was found not only in the patients' fæces but also on more remote skin sites such as hands, knees, groins, and the umbilicus. Resistance to gentamicin and many other antibiotics was R-factor mediated. Barrier nursing of colonised patients, stringent staff handwashing with chlorhexidine, and the use of disposable aprons seemed to contain the outbreak. Hand carriage was demonstrated in one nurse 62 days after she had left the ward.