To evaluate the value of B-type natriuretic peptide (BNP) in predicting the outcome of severe sepsis and septic shock patients. One hundred and two patients with severe sepsis and septic shock were prospectively observed. Plasma BNP level was measured at 24th hour after admission to intensive care unit (ICU) of a university hospital. The data of clinical features, 28-day mortality, acute physiology and chronic health evaluation II (APACHE II) scores and the length of stay (LOS) in ICU were collected. The patients were divided into survival group and non-survival group. The survival group was further divided into BNP elevated group and BNP normal group. APACHE II scores were significantly higher in non-survivors (39 patients) compared with survivors (63 patients, 28.9+/-5.9 vs. 20.2+/-5.4, P<0.01), but there were no statistical difference of white blood cell count and blood lactic levels between two groups. BNP levels were significantly higher in non-survivors compared with survivors [(1,451.3+/-531.7) ng/L vs. (394.5+/-81.7) ng/L, P<0.01]; BNP greater than 681.4 ng/L at first 24th hour was an independent indicator of mortality (sensitivity 91.4%, specificity 80.3%). In survivals, the LOS in ICU was significantly higher in BNP elevated group (48 patients) than BNP normal group [15 patients, (23.7+/-7.5) days vs. (14.9+/-5.1) days, P<0.05), but APACHE II scores showed no statistical difference between two groups. Plasma BNP level is a valuable prognostic factor for severe sepsis and septic shock patients.