The current measures for protection of the gas processing plant employees cannot fully prevent the impact of pollutants. Evaluation of the immune system is one of the methods for monitoring of the employees' health, and testing the system of measures used to improve the working conditions. The study was aimed to identify alterations in the immune status of the employees at the gas processing and high hydrogen sulfide content condensate processing facility depending on their working experience. The working environment and the employees' immune system were evaluated by standard methods. Pollutants were detected with the Bruel & Kjaer 1302 Multi-Gas Monitor, and the Tsvet-550 gas chromatographer. A total of 160 employees and 81 controls (blood donors of the regional blood transfusion station) were surveyed. The immune system was evaluated using the System 9000 Plus hematological analyser, Cyto FLEX LX flow cytometer, UNICO 2100UV specrophotometer, and KFK-3-03-ZОМЗ photometer. It was concluded that the existing complex of occupational and industrial hazards affects the immune status of the main production unit employees, which is reflected in the decreased CD20 levels and increased CD8 levels along with the constant levels of CD4. Correlations were revealed between the immuniglobuline level alterations, decrease in the phagocytic index and phagocytic number, as well in lysozyme activity, and the working experience. Pollutant exposure results in altered immunity of the employees, which could be considered the adaptation mechanism.