Background: We evaluated the new body fluid mode on the UF-1000i urinalysis analyzer for counting total white blood cells (WBC) and red blood cells (RBC) in continuous ambulatory peritoneal dialysis (CAPD), ascites and pleural fluids. Methods: We collected 154 body fluid samples, and compared the results of the UF-1000i BF mode with the Fuchs-Rosenthal counting chamber and the XN-1000 BF mode. Linearity, carry over and precision were also assessed. Results: Method comparison results showed acceptable WBC agreement between UF-1000i and chamber (y=1.27x+3.13, n=135, r=0.99) and between UF-1000i and XN (y=1.15x+0.31, n=135, r=1.00). Comparison between the UF-1000i and both comparison methods showed good agreement for RBC counts. Overall results were better when UF-1000i was compared with the XN-1000 than with the Fuchs-Rosenthal chamber. The lower limit of quantitation was defined at 9×106 WBC/L and at 25×106 RBC/L. Linearity for both WBC (r=1.00) and RBC (r=0.99) was good. Carry over was negligible, and it never exceeded 0.01%. In one sample, a high discrepancy was observed between WBC results for both automated analyzers and the counting chamber. This discrepancy was due to interfering factors, such as bacteria and yeast cells, and it led to a false increased WBC count on both automated systems. Conclusions: The UF-1000i BF mode offers rapid and reliable total WBC and RBC counts for initial screening of CAPD, ascites and pleural fluid, and can improve the workflow in a routine laboratory; however, when using automated analyzers, the inspection of scattergrams is required to ensure the most accurate results are obtained.