Background: A clinician reported unusually high incidence of A. xylosoxidans isolation from aspirated tissues in outpatient clinic. Methods: A. xylosoxidans isolates from January 2002 to June 2002 were investigated. The infection control nurse reviewed medical records and observed the procedures of tissue aspiration and culture at the clinical microbiology laboratory. Specimens were obtained for investigational cultures from dye, aspiration gun, slide alcohol sponge, tray, sink. water of sink, buffer solution, microscope, computer, and telephone. Results: A. xyloxosidans was isolated from twenty-four patients during 6 months. None of 24 cases had any typical signs or symptoms of infections by A. xylosoxidans. Observation of tissue aspiration and culture procedure revealed that buffer solution was used for prevention of specimen drying after tissue aspiration. Culture of the buffer solution yielded a heavy growth of A. xylosoxidans from four out of ten specimens. A. xylosoxidans was not isolated from any other investigational specimens. Conclusions: This was supposed to represent pseudoepidemic. Contaminated buffer solution was documented as the cause of this pseudoepidemic. The usage of buffer solution was stopped. During the follow-up period of 2 months, no additional A. Xylosoxidans was cultured from aspirated tissues.