Xanthomonas maltophilia infection is recognized as a serious problem in association with immunosuppressive and invasive therapies, and with the use of broad-spectrum antibiotics. In Darwin Hospital in Australia's Northern Territory preliminary evidence of nosocomial transmission of X. maltophilia prompted this retrospective examination of all X. maltophilia isolates over a 30 month period. X. maltophilia was most frequently isolated in the 'wet season' corresponding to times of increased antibiotic treatment of the serious community-acquired pneumonias encountered in this tropical region. A relatively high proportion of community-acquired isolates (4/18; 22%) was documented. This study demonstrates that X. maltophilia infection is an emerging cause of morbidity in tropical regions where endemic infections require the use of broad-spectrum beta-lactams.