The Klebsiella species form a heterogeneous group of gram negative, lactose fermenting, encapsulated, non-motile bacilli. They are important urinary tract pathogens, especially in long stay hospital patients and infection is often associated with urethral catheterisation. The laboratory characterisation of these organisms by biochemical means is time consuming and not entirely satisfactory. Antibiotic sensitivity tests indicate that gentamicin is the drug of choice for treatment of a urinary tract infection due to klebsiella.