A British hospital’s experience with a pseudomonas outbreak in a bone marrow transplant unit led it to warn against the use of chilled bottled water dispensers in such high risk areas. Pseudomonas infections are an important cause of morbidity and mortality in immunocompromised patients. Reporting to the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy in Boston, physicians at Queen's Medical Center, Nottingham University Hospital, Nottingham, described an outbreak of P. fluorescens caused by a contaminated drinking water dispenser. Over a one-month period they observed a sharp increase in P. fluorescens isolated from weekly pharyngeal surveillance swabs. Environmental samples were taken from a variety of sites including swabs of cleaning equipment, swabs from the nozzles of the drinking water dispensers, water samples of the drinking water supply, and water from randomly chosen wash hand basins throughout the unit. These were cultured onto cetrimide agar. Isolates were epidemiologically characterized by antibiotic susceptibility patterns, random amplification of polymorphic DNA PCR, and pulsed-field gel electrophoresis; all were identical. According to the investigators, nine patients became colonized with P. fluorescens. (None developed clinical illness.) All were in separate isolation rooms, each with en-suite facilities. A confluent growth of P. fluorescens was cultured after filtration of 100 ml of drinking water from one of two stand-alone water dispensers in the unit. The unit was shown to be heavily contaminated. All other environmental samples were negative, and there were no further cases of P. fluorescens colonization after the dispenser in question was removed. The investigators recommended that such bottled water supplies not be used in high risk areas, or are subject to regular microbiological monitoring.