In addition to capsular antigen typing and biotyping (sorbose, d-tartrate, dulcitol), the epidemiology of Klebsiella oxytoca can be improved by new biochemical characterization. The authors propose to determine tetrathionate-reductase activity, D-melezitose fermentation and brown pigment production onto a mineral gluconate-ferric citrate medium. In order to assess the value of these new markers, several hospital epidemiological surveys were performed in France and Spain (112 strains studied).