Objective: Review of the data on the number of positive and negative samples collected for the purpose of laboratory diagnosis of tuberculosis in the University Hospital of Split in the period from 01.01.2015. to 31.12.2019. Materials and methods: The retrospective study processed the data from the archives of the Clinical Institute of Microbiology and Parasitology of the University Hospital of Split and annual publications of the Tuberculosis Registry of the Epidemiology Service of the Croatian Institute of Public Health describing samples collected and analyzed at the University Hospital of Split for diagnostic confirmation of M. tuberculosis. The processed data refers to bronchoscopic, sputum, pleural puncture, cerebrospinal fluid, urine, lymph node puncture, tissue, wound swab and bone puncture samples. The data was processed in the Office 2016 software package (Microsoft, Redmond, WA). Results: From the total number of tested samples, the most samples were tested in 2015 (N = 2608), and the least in 2018 (N = 2104). The highest number of positive microscopy results was obtained in 2015 (N = 2114), and the lowest in 2017 (N = 1771). Accordingly, the highest number of positive cultivation results was obtained in 2015 (N = 2608) and the lowest in 2017 (N = 2104). Regarding the type of samples, the largest number of tested samples were bronchoscopic samples, followed by samples of sputum, urine and pleural punctures. Samples of cerebrospinal fluid, lymph node punctures, tissues and wound swabs were tested in significantly smaller numbers compared to the other samples. The average of positive results of microscopic and cultivation analysis of sputum samples and bronchoscopic samples, as well as cultivation analysis of pleural punctures, shows a slight decrease in the observed period. The highest number of M. tuberculosis isolates was confirmed in 2015 (N = 97), and the lowest in 2017 (N = 45). The antituberculosis susceptibility test identified 4 samples with isoniazid monoresistance in 2015, while no resistant samples were found in the other years. The test results indicate a decrease in the number of tuberculosis patients during the study period. Conclusion: The results of the research show a continuous decrease in the number of persons infected with tuberculosis in Split-Dalmatia County during the research period, as well as in the number of diagnostic samples analyzed in KBC Split, which is in line with the research hypothesis in the observed time period.