Alcaligenes xylosoxidans subsp. xylosoxidans (A. x. xylosoxidans) is a nonfermenting gram-negative peritrichous rod and opportunistic pathogen. The organism is frequently found in an aqueous environment. In the past few years, nosocomial infections caused by A. x. xylosoxidans have become more evident. The literature suggests that systemic infections are severe and often lethal and an optimal antibiotic therapy is not well established. This report describes nosocomial infections in 11 patients of a hematology ward over a 2-month period. Primary infection occurred during the neutropenic phase after cytotoxic chemotherapy. Reinfection spread from central venous catheters that had been implanted before the first infection. The bacteremia was successfully treated by imipenem. None of the 11 patients died from the bacteremia, but 3 died of their underlying diseases. Despite an intensive search for the source, the route of infection remained uncertain. Nosocomial infections by A. x. xylosoxidans are of growing importance in high-risk patients. Although the source of infection often remains unknown, infection seems to originate from contaminated solutions. Treatment with imipenem and the removal of central venous catheter systems successfully eliminated A. x. xylosoxidans, which adheres to plastic material.