In an attempt to further characterize infections due to Xanthomonas maltophilia, we reviewed 20 colonisations and 30 infections observed in our institution from january 1990 to december 1992, Xanthomonas maltophilia is emerging as an important nosocomial pathogen in immunocompromised patients, especially those receiving broad spectrum antimicrobial antibiotherapy. Distinction between colonisation and infection is often difficult. Xanthomonas maltophilia presents a therapeutic challenge because of its tendency to exhibit multiple resistance.