Objective: Our purpose was to characterize neutrophil degranulation activity related to the manifestation of preeclampsia. Materials and Methods: Studied were nine nonpregnant healthy women, nine normal pregnant women, and six cases with preeclampsia in the third trimester. Neutrophil preparations obtained for each case were divided into one nonstimulation and two stimulation groups using 10 and 100 nmol/L of N-formyl-methionyl-leucyl-phenylalanine (FMLP). Main Outcome Measure: beta-glucuronidase activity measured by fluorimetrical enzyme release assay was used for evaluating degranulation function. Results: (1) The total beta-glucuronidase activity in preeclampsia was significantly lower than in the other groups, whereas no difference was noted between the nonpregnant and the normal pregnant groups. (2) In the nonstimulation group, the degranulation proportional release in preeclampsia was significantly higher than in the other two subject groups, although there was no difference between the nonpregnant and normal pregnant subjects. (3) In the 10 nmol/L-FMLP stimulation group, preeclamptic women showed significantly higher values than those in the nonpregnant and normal pregnant groups. (4) In the 100 nmol/L-FMLP stimulation group, there was no significant difference in values among nonpregnant, normal pregnant, and preeclamptic women. Conclusions: These findings indicate that neutrophil degranulation is already activated in preeclampsia, with a decrease in the total granule content retained in neutrophil. This suggests that in preeclampsia, a possible modification mechanism exists, specific in neutrophil degranulation and different from the FMLP-induced O-2(-) producing system.