Data from a retrospective cohort study indicate that regular intravesical instillations of gentamicin reduce the frequency of recurrent UTI. A total of 27 patients with ≥6 culture-confirmed treatment-refractory UTIs in the past year received nightly intravesical gentamicin infusions. Systemic absorption of gentamicin was generally limited, and treatment was discontinued in patients whose serum gentamicin levels routinely reached >1 mg/l. No adverse effects were reported with use of this approach, and the majority of patients (22) had a decrease in the incidence of UTI after commencing treatment.