Purpose To compare hydroxyproline and nitric oxide levels, and fluid acidity between sac tissues from inguinal hernia, hydrocele and undescended testis patients. Material and method Thirty patients were in the inguinal hernia group, 11 patients in the hydrocele group and 5 patients in the undescended testis with inguinal hernia group. Intrasaccular fluid acidity, and nitric oxide and hydroxyproline levels in sac tissues were measured and analyzed statistically between groups. Results Intrasaccular fluid could be obtained from 24 inguinal hernia and 6 hydrocele patients. Acidity level (pH) was 7.5 ± 0.74 in the hernia group and 7.86 ± 0.63 in the hydrocele group (p < 0.05). All patients in the three groups were evaluated for nitric oxide and hydroxyproline. Results for hydroxyproline (mg/g dry tissue)/nitric oxide (nmol/g wet tissue) were 3.53 ± 0.54/2.02 ± 0.39 for inguinal hernia, 2.89 ± 0.9/1.92 ± 1.05 for hydrocele and 3.02 ± 1.23/2.86 ± 1.09 for undescended testis group (p > 0.05). Conclusion Hydroxyproline and nitric oxide pathways do not seem to be responsible for the different characteristics of inguinal diseases. However, differences in the acidity of sac fluid may be evidence of the different mechanisms of hernia and hydrocele formation.