Objectives: The aim of this study was to research correlation in the number of leukocytes in tracheal aspirates sampled in patients with various isolated pathogenic bacteria in relation to normal aspirates. Furthermore, the aim was to research the correlation between the number of leukocytes in tracheal aspirates and systemic inflammatory response, i.e. leukocyte levels and CRP levels, as well as the outcome of treatment. Study design: Cross-sectional study Patients and Methods: The study included 198 patients hospitalized at Intensive care unit of the Clinical Hospital Centre Osijek from 1st January 2018 to 31st December 2018, sampled for tracheal aspirates. The data were obtained from the disease history analysis, therapeutic lists and 443 tracheal aspirate samples. Pathogens were identified and the number of leukocytes in the aspirate sample was recorded. The data were compared with the systemic inflammatory response markers and the outcome of the treatment. The statistical methods used are: Student's t-test, Mann-Whitney test, χ2 test, Pearson correlation coefficient. All P values are twofold, and the level of significance is set at p<0.05. Results: Average age of patients was 65.29, and most patients at ICU were admitted to abdominal surgery. The majority of the samples were sterile, and the most common bacterium isolator was Acinetobacter baumanii. Statistically, there is a significant negative correlation between the number of leukocytes and CRP levels with the number of days spent at ICU (r = -0,172, P < 0,001). Patients with non-sterile aspiration findings are more likely to suffer from pneumonia (P < 0,001). Conclusion: The number of bacteria in tracheal aspirate is statistically significantly associated with the higher number of leukocytes in the aspirate. The number of leukocytes in aspirates was not statistically significantly associated with systemic inflammatory response and the treatment outcome.