To investigate the relationship between the inflammatory responses and postresuscitation syndrome, we prospectively examined the serial changes of neutrophil elastase (NE), urinary trypsin inhibitor (UTI), and TNF-alpha) in successfully resuscitated patients after out-of-hospital cardiac arrest. This study included 36 patients with out-of-hospital cardiac arrests who were admitted to our intensive care unit after return of spontaneous circulation (ROSC). The 11 patients who restored to spontaneous circulation within 30 min after cardiac arrest were defined as the short cardiac arrest group. The 25 patients who restored to spontaneous circulation more than 30 min after cardiac arrest were defined as the long cardiac arrest group. Eight healthy volunteers served as control group. Daily plasma levels of NE, UTI, and TNF-alpha were measured from days 1 to 5 after ROSC. The releases of NE from activated neutrophil just after ROSC in the patients with long cardiac arrest were statistically higher than those of the short cardiac arrest group. There was a significant correlation between the NE levels and the duration of cardiac arrest. A high but insufficient production of UTI for NE release was observed on day 1, especially in the patients with a long duration of cardiac arrest. The cerebral performance category of the short cardiac arrest group was better than that of the long cardiac arrest group. Although high levels of TNF-alpha were sustained in the postresuscitation period, the levels of TNF-alpha were unrelated to the duration of cardiac arrest. In conclusion, a massive release of NE in proportion to the duration of cardiac arrest and an insufficient production of UTI for the NE release may contribute to the pathogenesis of postresuscitation syndrome after out-of-hospital cardiac arrest.