Objective To measure the levels of neutrophil elastase (NE), citric acid and pH in prostatic fluid of patients with prostatitis type Ⅲ. Methods Fifty two patients with prostatitis type ⅢA, 98 patients with prostatitis type ⅢB and 105 health subjects were enrolled in the study. The levels of NE, citric acid and pH in prostatic fluid were measured; the expressed prostatic secretion(EPS)routine and bacterial culture were examined, and National Institutes of Health (NIH)-chronic prostatitis symptom index (NIH-CPSI) was evaluated. The data were analyzed by independent samples t-test. Results WBC count, NE and citric acid concentrations, pH in Ⅲ A group were (17.9±5.4)/HP, (898±704)μg/L and (14.5±1.7) ng/L, 7.60±0.43, respectively; those in ⅢB group were (3.9±2.2)/HP, (93±76)μg/L and (21.9±3.8) ng/L, 6.71±0.25, respectively; those in control group were (3.6±2.2)/HP, (86±57)μg/L and (22.5±3.9)ng/L, 6.48±0.51, respectively. There were significant differences in NE and citrate concentrations, pH value in EPS between Ⅲ A and Ⅲ B patients (t=8.22, 16.64 and 13.88, all P 0.05). There were significant differences in WBC count, NE and citric acid concentrations, pH in EPS, NIH-CPSI score between Ⅲ A and control groups (t=18.92, 8.47, 26.53, 18.37 and 32.47, all P 0.05), but there was significant difference in NIH-CPSI score between two groups (t=49.46, P<0.05). In EPS, NE concentration and WBC count were positively correlated with NIH-CPSI (r=0.819 and 0.698, respectively, all P<0.01), and citric acid was negatively correlated (r=-0.625, P<0.01); citrate was negatively correlated with WBC count, CPSI and pH value (r=-0.728, -0.644 and -0.817, all P<0.01). Conclusions The results indicate that the measurements of NE, citric acid and pH in EPS are of significant clinical value in patients with prostatitis type Ⅲ A and Ⅲ B. Key words: Prostatitis; Leukocyte elastase; Citric acid; pH value