To test the hypothesis that the use of protected specimen brushing (PSB) via flexible bronchoscopy does not predispose to bacteremia in ICU patients, we prospectively performed aerobic and anaerobic blood cultures immediately following bronchoscopy with PSB. A total of 123 episodes in 68 consecutive patients with suspected pneumonia were analyzed. Blood cultures were negative in 110 cases (89 percent) and positive in 13 cases (11 percent) (p < 0.001). Twelve of these 13 patients with positive blood cultures had quantitative PSB specimen cultures showing nonsignificant growth (< 10(3) CFU/ml). In nine patients, the bacteria recovered from blood cultures (coagulase-negative staphylococci or sarcina) were considered nonpathogenic according to conventional criteria. Blood cultures grew a Staphylococcus aureus in two patients with previously documented staphylococcal septicemia. In one patient with no identifiable site of infection, the blood culture yielded Enterococcus faecalis. The only patient with both a positive blood culture and PSB culture results indicating pneumonia had different organisms recovered from the two samples. Blood cultures taken after PSB in the 17 other episodes of pneumonia (PSB specimen cultures > or = 10(3) CFU/ml) were negative. At the time of brushing and blood sampling for culture, none of these patients was receiving antibiotics active on the organisms found. In conclusion, the incidence of bacteremia after PSB in ICU patients seems very low even in patients with documented pneumonia. Substantial savings would result from not performing routine blood cultures after PSB.