Norwegian hospitals are struggling to control spread of extended-spectrum beta-lactamase producing Enterobacteriaceae (ESBL-E) in health care settings. Strict screening and isolation criteria are enforced in hospital, and patients previously infected by ESBL-E are regarded as possible ESBL-E carriers indefinitely. This observational multi-centre cross-sectional study aims to estimate the duration of fecal ESBL-E carriage and to assess the risk of ESBL-E resurgence during hospital stay for patients previously infected by ESBL-E. Through better knowledge of these risk factors, infection control procedures may be better tailored to rhe individual patient.