Alcaligenes xylosoxidans is a catalase and oxidase positive, motile, nonfermentative and gram-negative rod bacterium. A. xylosoxidans infection is a rare cause of pulmonary infection and little information concerning treatment is available. The majority of patients that develop A. xylosoxidans infection belong to a high-risk group due to an immunocompromised condition or due to pulmonary cystic fibrosis. We report two rare cases of immunocompentent patients that developed a pulmonary infection due to A. xylosoxidans. A 77-year-old man was admitted with a lung abscess. The patient denied having any prior medical illness. A culture of bronchial washing fluid showed the presence of A. xylosoxidans. Despite appropriate antibiotic treatment, the patient died from acute respiratory distress syndrome (ARDS). Another patient, a 61-year-old man without an underlying disease, was admitted with empyema. Under the condition of a closed thoracostomy, a high fever persisted and the empyema was also aggravated. A. xylosoxidans was detected from a culture of pleural fluid. Susceptible antibiotic treatment was provided and surgical intervention was performed. We report these cases with a review of the literature.