BACKGROUND Cytological analysis of body fluids (BF) provides important information for diagnosis in various medical conditions. We evaluated the analytical performance of the UF-4000 BF mode for ascitic, cerebrospinal, pleural, synovial and continuous ambulatory peritoneal dialysis fluids compared to light microscopy counting (LM). METHODS 223 consecutive BF were analyzed by UF-4000 and results were compared using Pearson's correlation, Bland-Altman analysis, and contingence tests at relevant cut-off values. This study also included the evaluation of precision, linearity, and carryover. RESULTS For white and red blood cells (WBC, RBC) counts in all BF, correlation was excellent with Pearson's coefficients R2 > 0,98. Bland-Altman analysis didn't reveal significant differences with limited bias for WBC ranging from -10 to -1 WBC/µL and bias ranging from -43 to -6/µL for RBC. At specific cut-off values for WBC, Se and Spe were 100% except for ascites (Spe = 98%) due to two false positive. Precision evaluated at three concentration levels was good for each parameter (WBC < 10%). Linearity was excellent for WBC (R2 > 0,99) and carryover negligible (<0,004%). CONCLUSIONS UF-4000 BF mode is a good alternative to manual LM for BF cell counting. This automated method gives rapid and accurate results which is important for therapeutic decisions.