To determine changes in thiol/disulfide levels in patients with acute biliary pancreatitis for the first time, and to adapt these data to the clinic during the follow-up period. Evaluation was made of 39 acute biliary pancreatitis patients and 39 healthy control subjects. Amylase, lipase, and thiol/disulfide balance were determined from blood sampling. Prognostic markers were calculated from blood taken in the 48th hour of hospitalization of the patients. The Ranson criteria, APACHE scale, Imrei scale, C reactive protein, and procalcitonin values were calculated as prognostic markers. These were compared simultaneously with thiol/disulfide levels. Amylase and lipase levels were found to be significantly different in the experimental group compared with the control group, but there was no significant difference in the plasma thiol/disulfide balance. A minimally significant relationship was determined between C reactive protein and thiol/disulfide levels in terms of prognostic significance. The study results showed that the plasma thiol/disulfide level did not reveal the severity of acute pancreatitis. There is a need for more comprehensive studies to investigate in more detail the plasma thiol/disulfide balance which demonstrates oxidative stability.