A 5-month-old boy who suffered from a leukocyte chemotactic defect underwent flexible bronchoscopy for persistent right upper lobe atelectasis and tachypnea. Ten hours after the procedure he developed fulminant sepsis, and he died 16 hrs after bronchoscopy. Streptococcus pneumoniae (serotype 23) grew from the bronchoalveolar lavage fluid and from the blood culture taken during the sepsis work-up. We, therefore, suggest administering prophylactic antimicrobial therapy immediately following bronchoscopy to immunosuppressed children, even when an acute respiratory infection is not suspected, in order to prevent bacteremia and sepsis.