Introduction. Currently there are no relevant findings from a comparative study of the chemical composition of the abscess fluid and blood serum.The aim of the research was to study the composition of procalcitonin (PCT) contained in the blood serum and abscess fluids of the soft tissues and the abdominal cavity in local inflammation and sepsis.Materials and methods. The PCT concentration was determined in blood serum and the content of abscesses of the soft tissues and abdominal cavity in 45 patients of the surgical department. The experimental group included 31 patients with inflammatory processes that did not result in the organ failure. The comparison group included 14 patients with abscesses which manifested clinical and laboratory signs of the systemic inflammation and organ failure. The control group included 25 healthy individuals. The PCT level was determined by ELISA using the Procalcitonin - ELISA - BEST test system (Vector - Best, Russia).Results. Differences in the PCT content in the serum between groups were characterized by a high degree of statistical significance (H = 58.79206, p = 0.0000). The highest PCT level in the serum was observed in patients of the comparison group, where the average values were 11.94 4.98 ng / ml, the lowest PCT level in the serum was observed in patients of the control group. The PCT concentration in the content of abscesses was lower compared to blood serum and was characterized by statistically significant differences in patients of both - experimental group and comparison groups (p = 0.00001)Conclusion. Abscesses of the soft tissues and the abdominal cavity without signs of generalized infection are not accompanied by an increase in the PCT concentration in the blood serum for more than 2 ng/ml. The PCT concentration in the content of abscesses was lower than its content in the blood serum in both - the local inflammatory process and in the development of sepsis.