Background: Analysis of body fluids provides important information for assessing various rnmedical conditions. Bothe manual and automated hematology analyzers are used for cellrncounting. However, no published study is available to validate the diagnostic performance of thernSysmex 4000-i (Sysmex, Japan) system for the analysis of CSF and Pleural fluids. rnObjective: To compare the manual counts of cerebrospinal fluids (CSF) and pleural fluids (PF)rnwith the Sysmex XT-4000i automated hematology analyzers.rnMethods: In this cross-sectional study, 240 body fluid samples were analyzed using the Sysmexrn4000-i system in the body fluid mode and light microscopy at Tikur Anbessa SpecializedrnHospital. Body fluids included were pleural and cerebrospinal fluid (CSF). The results of thernmanual and automated counts were compared using the Pearson correlation test.rnResults: A comparison between the Sysmex 4000-i system and manual counting demonstratedrngreat correlations with regard to pleural fluid WBC, Polymorph nuclear cells and Mono nuclearrncell counts where r =0.82, 0.96, 0.95, respectively in both methods of the counts. Cell count fromrnCSF also showed good correlations for both manual and automated counts of WBC, PMN % andrnMN% where r=0.83, 0.94, and 0.92, respectively. The Sysmex 4000-i system also demonstratedrngood performance for differential cell counting (r =0.9028). CSF particularly showed a goodrncorrelation. rnConclusions: The use of the Sysmex 4000-i system for cell counting and differential analysis ofrnbody fluid samples might be an effective and automated alternative to chamber counting inrnlaboratory routine analysis, thereby enhancing laboratory workflow and clinical effectiveness.