Objective To investigate the respiratory burst function of neutrophils in very low birth weight infants (VLBWI).Methods Twenty two VLBWI was divided into two groups:neonatal respiratory distress syndrome (NRDS) and non NRDS (11 in each).The respiratory burst function of neutrophils in the peripheral blood of VLBWI within 48 hours after birth was determined using the flow cytometrydihydrorhodamine 1,2,3 method before and after the chemical stimulation of phorbol-12-myrismte 14 acetate (PMA),and the gp91Phox was also measured in resting neutrophils by flow cytometry.Twenty healthy term neonates served as controls.Mann-Whitney U test was used for statistical analysis.Results Before the stimulation of PMA,the percentage of activated neutrophils of VLBWI [(49.10±20.19) ％] producing a respiratory burst was higher than that of term neonates [(18.73 ±6.81) ％] (Z--4.911,P=0.000),however,after the stimulation of PMA,the percentage of activated neutrophils of VLBWI [(96.58 ± 3.44) ％] was lower than that of term neonates [(99.20±0.62) ％] (Z--3.186,P=0.001),and the stimulation index (SI) of VLBWI (171.40 ± 103.35) was lower than that of term neonates (306.30 ± 138.47),with significant difference (Z=-3.413,P=0.001).The geometric mean of gp91Phox in VLBWI (21.66± 19.87) was higher compared with term neonates (19.60±8.03),however,the difference was not significant (P=0.350).The percentage of neutrophils that expressed gp91Phox [(56.11 ± 29.40) ％] was lower in VLBWI than that in term neonates [(80.14± 14.87) ％],with significant difference (Z=-2.374,P=0.018).Before the stimulation of PMA,the percentage of activated neutrophils of VLBWI with NRDS (63.40± 16.45) ％] was higher than that of VLBWI without NRDS [(34.80± 11.65) ％],with significant difference (Z=-3.382,P=0.001),the SI of VLBWI with NRDS (129.46 ± 75.36) was significantly lower than that of VLBWI without NRDS (213.35 ± 113.49) (Z=-2.331,P=0.020).Conclusions Neutrophils producing a respiratory burst in both VLBWI and term neonates are active without stimulation of PMA,while the phenomenon is more obvious in VLBWI.Neutrophils in VLBWI and term infants can be activated by the stimulation of PMA,and express gp91Phox.The activation and gp91Phox expression of neutrophils in VLBWI with NRDS tend to be lower than those in VLBWI without NRDS.