We performed a prospective cohort study to quantify the number of cases of patient-to-patient transmission of extended-spectrum beta-lactamase-producing Klebsiella species on perianal surveillance culture. Among 27 patients who acquired Klebsiella pneumoniae infection, 14 had infections (52%) that were due to patient-to-patient transmission, and 6 (22%) had a subsequent positive extended-spectrum beta-lactamase clinical culture results.