The aim of this study is to investigate the relationship between the resting level of superoxide anion (O2.) and liver cirrhosis (LC). The resting levels of superoxide anion in the whole blood of healthy controls and patients with compensated or decompensated LC were measured, by an ultra-sensitive chemiluminescence (CL) analyzer and lucigenin amplification. The assay system can be performed in the absence of leukocyte isolation and stimulant administration. The results showed that the blood CL levels of compensated cirrhotic patients (381.0 +/- 201.5 counts/10 s, mean +/- SD, n = 24) were similar to that of healthy controls (467.9 +/- 299.5 counts/10 s, n = 24). However, the blood CL levels of decompensated cirrhotic patients (2083.5 +/- 1462.4 counts/10 s, n = 24) were significantly greater than that of healthy controls and patients with compensated LC (both p < .001, Student's t-test). The correlation analysis revealed that the blood CL levels in cirrhotic patients were significantly correlated with serum concentrations of albumin (r = -0.65, p < .001) and total bilirubin (r = +0.42, p < .005). However, there was no significant correlation between the blood CL levels and serum levels of transaminases (GOT and GPT). These results suggest that blood levels of superoxide of decompensated cirrhotic patients were greater than those of healthy controls or compensated cirrhotic patients. Moreover, the increase of blood levels of superoxide in decompensated cirrhotic patients is related to the impairment of liver function but not to the inflammation.