Statement of the Problem: Thymol (2-isopropyl-5-methylphenol) is a natural monoterpene phenol,a derivative of p-cymene, and an isomer of carvacrol . It is one of the most important constituents of thyme essential oils, which have been used for centuries in traditional medicines of many nations. Acute pancreatitis (AP) is an inflammatory process of the pancreas, which exhibits a broad clinical spectrum and can be either mild or severe. Since AP is an inflammatory disorder, a complex cascade of immunological events, which affect both the pathogenesis and the progression of the disease, is developed . Thus, the aim of the present study was to investigate the potential modulatory properties of thymol on rat immune cell viability and activity after acute pancreatitis induction. Methodology: Acute pancreatitis was induced by injecting L-arginine in a single dose of 350 mg/100 g of body weight . Three experimental groups of animals (six rats per group) were treated per os 1 h before injection of L-arginine. Group I (control/vehicle-treated) received olive oil in a dose of 0.4 ml/kg, while groups II and III (thymol treated) received 50 and 100 mg/kg of thymol, respectively. Viability of peritoneal macrophages and bone marrow cells (BMCs) was evaluated in an MTTassay, while the functional characteristics of macrophages were tested in methylene blue and myeloperoxidase (MPO) assays. Findings: Thymol at the lower dose caused a statistically significant decrease in macrophage viability when compared to the viability of peritoneal cells isolated from rats with AP. The higher tested dose of thymol (100 mg/kg) showed BMCs viability increase in comparison to the viability of BMCs isolated from rats with AP. The macrophage adherence was increased after AP induction, but both tested doses of thymol statistically significant decreased this function of the immune cells. On the other hand, further results showed that MPO activity was increased in peritoneal macrophages after L-arginine injection. Thymol, in the higher dose, additionally increased the enzyme activity.In this study, we showed that thymol has the potential to modulate immune cell viability and functioning in an inï¬?ammatory reaction, such as the one seen during the course of AP.