In 1999, over a 3-week period, Alcaligenes xylosoxydans subsp. xylosoxydans was isolated from five blood cultures and one cerebrospinal fluid specimen from five children hospitalized in a pediatric hematology ward as well as from two respiratory therapy devices of two children hospitalized in an intensive care unit. The infection control unit of the hospital conducted an epidemiological investigation and identified a detergent-disinfectant solution as the source of contamination. Conventional biochemical tests, antimicrobial susceptibility tests and random amplified polymorphic DNA (RAPD) fingerprinting were used to compare clinical and environmental isolates. RAPD analysis proved to be more discriminant than biotyping or antibiotyping in this context and identified the common source of the outbreak.